1) Key prep spots for the basics (particularly: protection/flight)? Any other must-know shoppies for basic Outlander survival?
the potions from the gargoyles outside of Barovia do cancel and then protection, make sure to use them first when prepping so you don't cancel out something else
most builds who need flight preps buy them from merchants that fit RP-wise

2) How do you view group mates grabbing coins? Is that like quaffing a potion in presence of a villager?
up to your char/role, i've killed people for giving me coins on some outlanders and not given a fuk with others

3) Which merchants are okay to use and which aren't? Is any merchant (or guild) where not standing in a "wilderness room" is off limits?
it doesn't matter if the room is wilderness or not, look at the mob's race/class, the most obvious nono merchants are those in protected cities

4) Okay to use the healer at the Inn? What other non-cabal healers are your main go-to options at Outlander?
hell yeah! there's one in the weald too, and evermoon should be kosher... and I'm sure I'm forgetting other outlander friendly healers

5) What is general the dynamic between reavers and wardens? Do most fight each other often?
Open season. If it becomes too disruptive don't be surprised if an imm comes down and lays the smack. I've seen some that are friendly and others that want to remove the opposing branch completely.

6) Is Ancient Insticts a quest thing, like somehow a quest is initiated in game by some action the player takes? I kinda get what it does but I don't really get how it works at all, and I also get that you're not supposed to discuss but who do you ask or what should you do, at what rank does it come into play or is there some prereq to be aware of?
Not a quest thing, but still kind of nono to talk about elsewhere besides IC. The only prereq is getting to the level of the skill. It's not the same for all classes, like druids and rangers get it at lower level cuz they're much closer to nature. Look up some skill lists of premium battlefields to find out what the level is exactly, I forgot exactly what level but I think it'd mid level. Once you're at the level you need to find something that you should discuss IC.

7) Any other tips on what to do or not do as an Outlander, beyond the obvious?
Have fun, and don't take any shite from anyone. Life without coins is easy once you get the hang of it. Find expensive but lightweight treasures to keep in your sack to barter for healing. There's rings and gems and all kinds of stuff that weigh just one ounce that are worth all the way up to a heal heal. Hell I think the flickering gem from the campfire in Aratouldain are super light and worth a heal heal.