I'm not a doctor but here is some anecdotal evidence of what works for me.

I wouldn't worry about the model of bike you get but the way it fits you. You can easily adjust the stem, seat position, etc to change how any bike fits. If you're planning on doing long distance touring then by all means get a touring bike but don't fret over the different models. Some people with back problems prefer an upright bike with flat bars but like 10 Wheels, I find that riding drops increases my core strength and this in turn helps keep my back in line (pun intended). Only you can decide what type of bike will work for you.

Start really slow when you get riding again and I mean really slow. The temptation will be to jump right in and go but you need to be gentle with your body and give it time to adapt. I often go for long walks on the days I don't ride as a placeholder.

Stretch! Your leg bone is connected to your hip bone which is connected to your backbone. Tight hamstrings are fairly common for riders since the quads get so much use. Stretch your hamstrings, especially after riding, since tight hamstrings can cause strain on your back.

Relax. Tension can cause all sorts of back aggravation. Make some effort to consciously relax your muscles and your mind.

That's my back strategy and it's been working for me so far. I've come to realize my back will never be the same as it was when I was 20 but with a bit of care and thoughtfulness I'm planning to keep it healthy enough to not be a limiting factor.