Hi Hobbling
I'm probably not best placed to advise, I've been practicing yoga since Jan 16. My experience has been Yoga with Adriene (which I think tends to Hatha), and my local classes which doesn't align itself to a particular type (its brand is My Kind of Yoga, so a bit like Adriene I guess, in finding what works for you).
- I think Ashtanga is well know for strength as well as flexibility, Hatha concentrates a lot on breathing while holding the poses for longer? Don't know how Iyengar fits in.
- I suspect you'll start to work out a particular class that you just prefer attending.
- The more you do, the more benefit you'll gain. I practise yoga, but also see a PT for circuit training, do some weights at home, occasionally run. Certainly when I'm practising yoga more frequently at home, I notice it in classes.
- I tend to use Yoga with Adriene You Tube videos as I like to have some structure to my home practice. You do definitely get to know the moves and sequences, so I tend to practise with my eyes shut. I would definitely make sure you're familiar with poses from class before doing too much at home, but I have to say, Adriene is very good at describing how it should be feeling, and always make sure you're listening to what your body's telling you.
Good luck and enjoy. I wasn't convinced I'd like yoga when I started, thought it was all a bit wishy-washy and I wouldn't work hard enough. Not true!! I really enjoy my classes, they're the only exercise that I actually feel is me time, the other stuff always feels a bit chore-like.