There is no single best playstyle for unMonk throughout all levels, check my unMonk DPR calculator for exact numbers and a comparison throughout levels 1-16.
There is a pretty nice guide, although it has some notable issues, so I'm gonna give my take on the most important aspects:
Before anything, you probably should decide on whether you want to sue a weapon or not. UnMonk is proficient with every weapon with the monk special property, so there's plenty of choices. Upsided of weapons compared to unarmed are cheap enchantment cost (although unamed can use handwraps instead of the classic Amulet of Mighty Fist, if you are OK with not getting the bonus on some style strikes), the ability to use them two-handed for both 1.5xStr (that was changed from cMonk) and 3:1 Power Attack ration, the ability to have reach, and the ability to have different damage types. The downsides are that you can't use the bonus attack from spending ki, or style strikes, with weapons (unless you have the Ascetic Form feat, see below for more on that). That doesn't mean armed builds can't use them, though - they can use an unarmed strike (usually the bonus attack from ki pool) to make the style strike and attack with the weapon the other attacks, which is something especially worthwhile for Flying Kick.
Archetypes:
Unlike cMonk, UnMonk is a fully functional class without archetypes, but there are some that are worth looking at:
Brazen Disciple replaces Still Mind and some bonus feats with bluff/feint stuff.
Invested Regent replaces the first bonus feat to grant you additional spell-like abilities in place of feats (bonus or regular), your pool won't be overly large but some of these SLAs are rather nice (e.g. Air Walk at 10th level).
Perfect Scolar replaces Still Mind and the 4th level ki power with a bonus to knowledges and a cute little accuracy boost.
Soul Sheperd replaces Stunning Fist and Evasion with DR and resistances.
Windstep Master replaces the 4th level ki power with the ability to walk on air. Already pretty nice, especially when you don't plan on taking Empty Body early on, it get's to almost must-take levels if your GM allows you to make Flying Kicks while in the air (RAW is very unclear, but they are called "flying" kicks after all!).
Feats: Apart from the archetype, your most important choice is probably ging to be which style chain/VMC you use.
The "normal" paths would be Ascetic Style, Dragon Style, Jabbing Style, VMC Barbarian, VMC Magus, or using none of the above. Apart from Dragon Style, they all also work with Weapon Finesse, although VMC Barbarian only if you take unchained Barbarian as a base.
The easiest method is Styleless, i.e. not using any style feat chain at all and instead grabbing assorted feats like Power Attack and Possessed Hand - it's not much weaker (at some early levels even stronger) than other styles and allows greater flexibility. This is possible both with a weapon and unarmed strikes.
Ascetic Style (up to Ascetic Form) is something like the default style for armed - it's not exactly necessary, but it is much smoother (and more flavorful) than weapon based styleless, and it's also the highest damage non-VMC style. You basically get all the goodies of both armed and unarmed (including ki pool's DR penetration ability, and even the scaling damage), for the cost of a few feats. Armed only.
Dragon Style (up to Dragon Ferocity) is something like the default style for unarmed - low investment (only two feats) and comes online very early (3rd level). Unarmed only.
Jabbing Style (up to Jabbing Master) depends a bit on the enemies - the higher the AC, the weaker it is. Also needs four feats and only becomes good at 9th, but can do a lot of damage if the enemies aren't particularly high-AC ones. Unarmed only.
VMC Barbarian takes even more feats (every other feat, plus you probably want Extra Rage) and lowers your AC, but it comes online early (3rd level), and has some nice additional benefits (well, it's Rage), including a Rage Power at 11th level. Armed or unarmed.
VMC Magus takes at least as many feats (you definitely want Extra Arcana, the Magus Arcana you get at 7th level will be Ki Arcana), comes partially online at 3rd level, but becomes truly crazy at 10th level, when you can basically make every attack against touch AC by (ab)using Accurate Strike and the Ki Leech ki power. Armed or unarmed.
Bonus Feats: The stand out ones are Dodge, Deflect Arrows, and Medusa's Wrath, plus depending on campaign, build, and allies, Mobility and Combat Expertise. Improved Critical is the only one to directly increase your damage, but it's really weak at that.
Style Strikes: Your first or second style strike will be Flying Kick, period (the only exception would be if you expect lots of open battle field fights with enemies pretty far apart, and you want to use Pummeling Charge). It takes a while to be really good, which is why selecting it at 9th level is OK, especially when you aren't constantly dungeon crawling.
Elbow Smash (more damage) and Foot Stomp (prevents escape; including 5-feet-steps) are also pretty nice.
Ki Powers: There are too many ki powers to list all the good ones. Depending on your build and campaign, the best are often these: Empty Body (yes, you can really select it at 4th level, and it grants amazing versatility to a character normally lacking exactly that), Barkskin, Placebo Effect, Restoration, Freedom of Movement, Insightful Wisdom, Ki Leech, Dust Form, and Diamond Soul.
Equipment: At early levels, you'll probably want to use one of the three monk reach weapons, Double-chained Kama, Kusarigama, and Kyoketsu shoge. All are weird, but Kusarigama and Kyoketsu shoge also have two different damage types. Since Flying Kick requires you to end adjacent to the enemy, you'll want to use a non-reach weapon later on, you might just want to start with one as well, in this case Sansetsukon or Seven-branched Sword have the highest base damage (Sansetsukon is slightly superiour because 19-20/x2 is better than 20/x3). It's possible to flurry any melee weapon by using the Versatile Design weapon modification and Ascetic Form, but you need to spend a feat or two on proficiency, and mechanically, it's usually not worth it. For unarmed, you're stuck with Handwraps were mentioned, or the twice-as-expansive-to-enchant Amulet of Mighty Fists (which also blocks your neck slot, so you'd probably want the Barkskin ki power).
Weapon Finesse based builds can go either unarmed, or use weapons, the best ones are Sanpkhang and Cestus. If not using Ascetic Style, the best weapon is Waveblade.
Something of a 'must have' item is a Wand of Mage Armor, handed to an arcane caster of your choice. You an be generous with the charges, as your caster buddy should have 1st level spell slots to spare by the time you've used them all.
Multiclassing: Multiclassing is, of course, possible. UnMonk does gain quite a lot, though - bonus attack at 11th level, ki powers that can be very strong (like Ki Leech at 10th level), and style strikes/ improved Flying Kick range. A dip into Bloodrager would be Ok, but I wouldn't recommend lowering your accuracy by dipping into a non-full-BAB class.
I would take the Dual Talent alternative racial trait to give you another +2 to put into Strength to bump it to 18.
Depends a bit on the chosen style. You need the bonus feat to get Ascetic Form at 5th level, for instance.
that tri-point sword with reach
Tri-point Double-edged Sword (what a mouthful, and it isn't even an actual sword) - it's in the monk weapon group, but not a monk weapon, so you need Ascetic Form to Flurry with it. As mentioned, you can't use Flying Kick with a reach weapon, so there isn't really a spot where you'd want to use that weapon.
The Weapon Adept archetype MIGHT fit uMonk, I've heard it both ways.
Not RAW - no pre-Unchained Monk archetypes are allowed for unMonk, and only those post-Unchained ones that explicitly say so. UnMonk certainly doesn't need it, anyway, the class is very fine (for a martial) as it is.