Hell yea Matt glad you want to get back into biking! Might as well have a bike on the back of the Prius! 👍
+Bike=
Having only 1 bike for the rest of eternity is a hard decision to make. Ive had everything from 20" Bmx, 24" Bmx cruiser, 26" mountain, 29" mountain, fixie road, and other road bike combos. My advice is this; ask yourself what are you going to do with the bike? Short tour, long tour, day tour? Mostly pavement? Lots of gravel? This all comes into question, as you already know. My suggestion is to go to a bike shop and ride a few bikes for free, different styles. See what you really like. Then search Craigslist or FB marketplace for a style of bike you want. People tend to go buy a new bike and then not ride it and sell it for a fraction of the cost of new. This way you can upgrade parts on a "used" bike to your liking without having to basically throw brand new parts away.
I prefer 26" tires for many reasons already said. 29" tires are just goofy and unnecessary. Don't buy 29" tire bike. I also prefer the ergonomics of a more mountain bike style bike. These 2 personal preferences of mine are because I like riding gravel and dirt. I've road some distance on pavement on 26"x2.5" dirt tires, and its deff not as efficient as a skinny gravel tire, but it's managable. Just air them up good. It's nice being able to roll over rocks on the road and not worry about your tires popping. Plus you can ramp up curbs and blast over train tracks without worry.
You can put any handle bar on any bike pretty much with the right parts. Being able to change your grip position when touring is a must. You can get add on handle pieces for the bars also, if you go with a straight bar mountain bike style bar.
Disc brakes are a fairly new thing in the bike world. Higher end sets work awesome. I had hydraulic discs on my Kona, and they were scary good. I do not recommend hydraulic though, as they will eventually leak and need attention, which could get pricey. Lots of people swear by the older style rim V-brakes (by Avid I think) that they are every bit as good as discs. I agree, V-brakes stop on a dime as well.
Look for something with really good components (shifters/derailuers) already installed so you don't have to upgrade. I'm a fan of Shimano deore stuff. Not the best but solid. I hate grip shifts, stick with triggers or levers.
If you end up with a bike with a front suspension fork, make sure it's a higher end one with a lock-out for pavement riding. Fox probably makes the best suspension forks right now.
Most importantly though is that the bike is comfortable for you to ride. I would test ride a bike at least 5 miles to get the feel for it. Have a bike shop properly size you up for a bike so you know what size to look for. Good luck on your bike hunt! Can't wait to see what you decide on!