Short term hinges on whether they truly only care about performance and what that means.
You have an idea in your mind of what good performance is. They may have an entirely different one. Most companies claim to only care about performance for developers. The problem is, the definition of performance is entirely subjective. It could be based on features ...
I'd like to stay here, but I feel like I'm really not a fit.
Naturally, everyone else gets way more done than me, though I'm very
happy with what I get done during the normal working day. My manager
acts pretty much like these other engineers, and he's said performance
reviews will be strictly performance-based, but his higher-up manager
has said ...
You are looking for a wrong thing in the wrong place.
You either looking for a job that, per se, requires you to think "the-other-way-around" while being a computer programming job. A problem solver. And almost no company like to admit they have problems so this is type of consultant job. It even help to get someone from outside to have a fresh look.
culture better matches this my "what-if" style
Well, that is difficult, I know from experience. No matter how interesting and useful it is to think out-of-the-box, most of the people think inside-the-box, and many times, the box is actually quite small.
I was faced with two choices:
Keep talking out of the box, alienating everybody, family included;
This shouldn't be a problem and you shouldn't make it into one.
Carry on as normal. Drive to work, do your work, drive home from work. Say thank you to those that complement the car. If you're that worried about them judging you for having bought a more expensive vehicle, just add an 'I've been saving for a while and excited to finally get it!'. You don't ...