The ultimate cop out line of, it all depends on your party with the small stuff. For the party that is likely going to really dig into the small stuff, they are the right people for the sandbox of Kingmaker.
Personal experience wise:
Hexploration - This becomes a small thing likely around the end of book 2. I'm guessing the broad strokes of exploration won't be handled by the true party moving forward and they'll just go hit the big things.
Money at Oleg's - a huge deal, especially if the party has a number of mounts with them and are looting everything in sight.
Weather and things by the side of the road - definitely a way to help keep the hexploration from getting dull
Food - a good way for the character(s) with survival to show off a little and help feed the party while on the road.
If anyone has some opinions on the rough types and numbers of buildings for Pitax, I would be curious to see them. My party just finished up book 2 and found some things with Hargulka that is making them do some initial espionage looking at Pitax which give things like their overall national health and the like.
Also, while I love the look of that huge map, it doesn't match up with the hex maps provided...so if you were going to use it you would have to do so from the beginning which is sad because it is the best looking of them.
Granted my party just started book 2, but even with 5 party members, they had done a pretty good job and keeping WBL in check.
If you are behind there are two ways to get money for an adventurer, go out and smash some monsters or get a job, aka downtime rules. If you have been completing the quests as they pop up I would think you should be pretty well in line, but if not I can totally see how players are not on an even level.
Bring it up with the GM and have them drop a couple more quests in, it is an easy way to have the party go out and pull in some cash without unbalancing things too much.
Owlbear as a mount would be very odd, partially because bipedal. Run into an issue as well in that they are magical beasts and not a vanilla animal.
If you have enough catfolk that they are looking for a large group then importing in lion or tigers would make sense. With the terrain up here as well as the weather, tigers would fit better. Trick on an animal like that is if you have a stable of them, you have issues feeding the things.
Though a little late for this game, something my friends and I have been doing in recent games is using Obsidian Portal or something similar to have someone from the group post an adventure log for every session. We then give the party an XP reward for their average level for a post. Helps keep everyone in, a good write up going and can help even out some of the xp bumps.
First off I love the crap out of this idea. I think the biggest thing with this is to keep the bonuses they receive either very minor or fairly rare. Also, look at making some of those secrets need not just BP but also time to fully unlock. Or have some of it be like gated by time unlocks.
Might be a lot of crazy book keeping but has some great possibilities.
KenderKin I was thinking much the same thing. Also trying to group and stack encounters because one of the biggest things I've been reading is that the whole aspect of one encounter a day just completely dilutes things. Tools to help drop hints or foreshadow the different aspects I would think are the bigger thing. With leveling being more of a framework and reward rather than, where here is this hexes fight.
The problem is you can't simply let people expend energy to counter. Because anything to do works both ways and "simplifying" the system only allows you to frustrate a player to no end.
I have never had a problem with it being a conscious choice that a caster takes themselves out of initiative basically to sit there and prep to counter. Also, Dispel Magic and Greater dispel are there for a reason and should not be ignored as spells.
It is the classic one wizard staring down the other and just swatting things aside. They aren't throwing their own in between. It is stare and swat and that goes back and forth. A lot of staring and gambling.
I did the same as Kellfox with the sylph. There was no reason for the PCs to go all out and the pally in the group wouldn't let them attack unless they were attacked first. They bantered and she left. Granted, left to go warn people but left.
Bringing the Radosek fight down and out into the courtyard is a major combat change and one that can definitely ratchet things up for the PCs who often times especially at low levels are going to do better with the tower's smaller rooms.
Kobolds and Mites convert fairly well actually, just treat it more like a minor house or Hatfield and McCoy type of situation. Little bit of backwoods to it and they will work just fine.
With Fey involved still and humans are humans, most of that should just dovetail in. No reason a pseudodragon can't be an odd fey creature.
I really like the idea of keeping the story going between the different campaigns, especially when a group has been involved because you increase that feeling of ownership. And while I don't want to rule out running some of the APs, having some of that metagame continuing plot helps with world immersion as well.
Something else that would be fun is an AP set out on Triaxus. We visit it for one book in Reign of Winter but in this secondary world, there is the big setup for a lot of draconic fun. Not sure how you get the party there but we would have a few options and that has really the best spin on draconic interaction out there.
See, That is exactly why I love this AP. You never see this kind of stuff coming but can have an awesome impact down the road. Great RP action there.
My best suggestion is to play the bad guys smart. Have them group up or prep possibly better than before. If the party is having an easy time of it some additional prep or combined encounters can be key. Make them switch up tactics every now and then. Tricky part is letting the PCs shine while still giving them challenges.
The same kind of shared editing is available on other platforms, like OneDrive but it is all a matter of personal preference.
As for cities, I wouldn't think you would have too many either. Especially in the terms of Kingmaker. If you were trying to use a sheet to do like Brevoy you might run into issues, but for building it out looks awesome. I know it is a lot of work to build these things.
Content wise I like it. My biggest beef with it is more aesthetic than anything really. Nothing saying you can't use a full Excel doc in a Goggle Drive share, just might not be able to edit it directly from there.