To echo Chewy, your test should be a good indicator of which machine you need. Even then there are options. I've had 3 over the years and I'll just suggest getting the quietest one possible. Also consider portability as you'll want to take it with you when you travel and the easier it is to haul and set up, the better.
Mask is key. When you go for your fitting, try on as many as you need to find one that's as comfortable as possible. How you sleep will be a big factor. I use a nose only mask like the first one on Chewy's post. It works for me as i'm primarily a side (80%) and back (20%) sleeper, but lot's of people don't like them. Take your time when you do your fitting and try each kind. You can get a new mask fairly inexpensively if you need to, but insurance generally only pays for 1 per year.
I does take a week or two to get used to it, but stick to it. It really makes a bid difference in your quality of life it you use it every night and will benefit your heart greatly over time.