Disciple of the Pike Cavalier gets Weapon Training specifically in polearms and spears.
Arsenal Chaplain Warpriest gets Weapon Training and bonus feats and spells.
And, my favorite, the Arcane Duelist Bard with a +1 Impervious Whipwood Longspear, Combat Reflexes, Flagbearer, the Banner of Ancient Kings, a Dervish Sikke, and the Gloves of Arcane Striking.
I’m playing an Oracle with the metal mystery and polearm/shield feats. It may not be the most optimised character, but it can do things other than just hit people.
Shield Brace takes two feats, and you'll want Power Attack and Combat Expertise. You'll want proficiency with shields (to not delay the build further), and martial weapon prof or prof with deity's favored weapon (as there is no simple polearm). A bonus feat would be nice, but isn't essential.
There's a lot of classes and archetypes that fit the above mentioned. Your desired playstyle doesn't demand something specific, so you can fairly freely pick. And even something without proficiency, like Investigator, would easily be made to work with a single level dip into Fighter.
Oh yeah, you want to use a shield, too... well then, Phalanx Soldier Fighter (or at least 3 levels of it) might be worth it. I know you didn't want a Fighter, but...
Phalanx Fighting (Ex)
At 3rd level, when a phalanx soldier wields a shield, he can use any polearm or spear of his size as a one-handed weapon.
This ability replaces armor training 1.
Sohei Monk also gets Weapon Training with polearms being a choice... they can Flurry with anything they have Weapon Training in, too. Unhindering Shield would allow a buckler to not interfere with your Monk stuffs.
Gorum has a trait [Shield Trained] that makes heavy shields count as light weapons... if you want some crazy TWF shenanigans to go with using a polearm as a one-handed weapon.
Occultist. Probably Trappings of the Warrior, but you don't actually Need full BAB to be a great front-line fighter as an Occultist.
As others have said, Shield Brace and Combat Reflexes are your mandatory feats. You can actually skip Power Attack until later since the damage boost from Legacy Weapon is often way more potent than Power Attack, and the penalty to hit isn't worth it until the damage bonus is bigger. Since you're using Psychic magic you also don't have to worry about Somatic Components.
I'm more looking for classes or more so archetype that grant bonuses or fun ability for using a Pole-arm and can use a shield
You don't need to. Apart from Magus, every class suited for melee works, although some require additional investment (e.g. a dip or an extra feat ).
Seriously, you shouldn't limit yourself to archetypes that explicitly mention polearms. Polearm Master is worse than regular Fighter, and while Disciple of the Pike isn't a bad archetype, the class itself is bad.
Don't focus on whether or not an archetype contains the word "polearm", but rather think about what you want. What do you want your character be able to do?
One word of caution:
Using a non Buckler shield and a Reach weapon likely means that you cant easily cast spells with somatic components, keep this in mind when decided on your actual class.
Nah, you can ungrip the other hand from the weapon, use it to cast a spell or drink an extract, and then regrab the weapon with that hand.
Oh one more feat for any reach-weapon user - LUNGE.
Enemies who move to you provoke AoOs , but if you move to an enemy and attack them then they're free to 5-foot-step in and full attack you. With Lunge you can attack them from 15 feet away, which means if they want to return fire they have to move in and provoke .
You can get around the need for this feat with good positioning and readied actions, and it's less necessary for casting classes , but honestly even then you'll still find it useful.
The main benefit of a reach weapon is the ability to generate AoOs as enemies move around/toward you. The benefit of Lunge for a reach user is that you can attack enemies on your turn without giving up that benefit.
Yes if you go all in with archetypes, spells and feats you can give yourself 30 foot reach and a bajillion attacks, but Lunge is a single feat that gives a large return for such a small investment for a reach user.
12 DEX, Combat Reflexes and Lunge will see you through 90% of the encounters you face. Don't feel you need more than that.
I currently play 2 characters who use reach tactics: a 13th level Aberrant Bloodrager and an 8th level Occultist with a reach weapon. Both characters are the only front-line character in the party, and my main tactic with both is to stand between the enemy and the casters and make life difficult for charging enemies.
Until a couple of weeks ago I could count on 1 hand the number of encounters where having more than 2 AoOs available would have made a difference .
It looks good on paper to have 30 feet of reach and 12 AoOs per turn, but you absolutely don't need it. I personally prefer 14 DEX because sometimes that extra AoO is clutch, but my Bloodrager has never had more than 2/round and he's been a Very effective protector for the party.
Honestly, I feel like we're derailing the thread at this point.
I guess the OP has two examples of how necessary they are, and can use our experience to help them work out what they need.
As far as house-ruling Combat Reflexes to limit the number of AoOs, I've thought about it. I think it would probably be balanced if you limited the extra attacks to HALF your DEX bonus . This would mean your 20 DEX character with an Elven Branched Spear would only get 3 AoOs , but the "minimum 1" would make it a more useful feat for everyone.
Also I personally don't think any nerf is really needed but I think it'd still be a good feat with those rules and any GM who's having trouble with it would be able to manage it more easily.