Recommend 5x5 stronglifts ... not because it's a particularly good program (it's not - it's too easy to burn out early), but because it's a good resource to learn the main lifts initially. Lots of photos and explanations all in one place to make it as easy as possible for the new lifter.
I have used the 5x5 program and while I'm not here to endorse any particular program, I found that I really liked it. It did help me learn proper form, as you say, and it also gave me a very regular workout. I had it memorized and it always uses the same part of the gym (squat rack) so it helped me maintain a rhythm.
I actually built a squat rack at home eventually to start it back up after some time away.
There may be better programs, I have not actually tried any others. 5x5 was the most-recommended I found in my research a few years back.
Also, GGP, lifting did correct my posture very quickly. People kept telling me I looked taller/stronger/wider even before anyone knew I was working out (and before I had actually gained any muscle), and I'm quite sure that was just my improved posture.
Yeah - mental. You reach your maxes quickly and progression gets difficult because you're trying to do so much in a single session, but you don't need to think about other programs while you're still making progress with what you're currently doing.
The other thing for me was it started to take too long - I generally try to get my stuff done in an hour or so before work. I went from SL to GSLP to 531 (3 main lifts, to 2, finally to 1, per session).
To be honest, I don't think it matters too much - as long as you find something you like to do enough to stick to regularly, you'll improve in health and posture either way.
I always found that I could get my lifts in in about 45 minutes. It can be slower with a partner if their weight is very different from yours, because you're moving weight on and off a lot the bar, but ours was small enough that it wasn't a major time concern.
Later I did it solo and my workout times were ~30 minutes for the quick day, and ~45 minutes for the long day. The long day being squat/bench/row, and I felt like my breather periods were very generous.
https://stronglifts.com/5x5/