Everyone else has provided excellent answers but I'll give it a go too

-DD has been getting nappy rash It's better since I stopped using wipes and just started using a cloth and water, but it's still there a bit so I was thinking it might be from the chemicals in the nappies So, do you get less nappy rash with MCNs?
We get less rashes here because the kids react immediately to the chemicals in sposies. We still get rashes - but only when teething. Plus the creams you use with MCN's are much less toxic than the creams you can use with sposies. That sounds good to me!

-I like the idea of AIOs, the easier the better! But when you say they take longer to dry, how long? And are they ok for newborns and the poo that can escape anything!!
Ok for newborn poo explosions - leg gussets are your friend. Most AIO's don't come with leg gussets, so there is a chance for a total explosion to erupt!!! You could look into AI2's like the pop in which come with leg gussets though and are pretty quick drying too. My AIO's take 2 days to dry - but I dry them inside. The quickest ones to dry that I have found are the Bumgenius AIO's and the Monkey Doodlez AIO's.

-I want to get OSFM bc I don't want to be spending heaps of money buying new ones every time she grows out of them but will they fit her now?? Or should I wait to start using them til she's a bit bigger?
You might be lucky and get ones that fit her now. THe Pop in is excellent for younger bubbies. If she has chubby thighs you should mostly be ok, because the main problem in fitting is the leg gape - which you get with skinny chicken legged bubs. Oh - and they are more bulky too - so don't forget that. If you are after a trim nappy - I wouldn't necessary go for a OSFM.

What brands do you recommend? DD is a chubby bubby, not skinny at all, lol. What ones would fit her shape best?
Totally depends on whether she can suit a wide crotch or not. My kids are more trimmer crotch kids - but they can do a wide crotch as well - they get slight "camel toe" action but the nappies don't leak.

I would recommend heaps, but I have favourites that go from fitteds, covers, pockets, AIO's and AI2's.

All off them have their pros and cons of course.

HTH!!!