I think any bottle would be fine for a newborn. With our foster babies we plan to use the simple glass Evenflo bottles (3 for $5 at Walmart or Target). Inexpensive and easy to clean, and won't retain a smell if we forget to wash one.
I'm pretty certain that Avent bottles need Avent nipples.
I don't think it matters whether you use liquid or powder. It just depends on personal preference, I think. I would think that powder would be faster b/c you can start with warm water, whereas with liquid you have to keep it in the fridge (unless you get individual size) and you'd need to warm it up. In the middle of the night, I'm not sure I'd want to deal with that. Kwim? Liquid is also MUCH stinkier than powder is. Powdered formula, imo, doesn't have much of a scent, but liquid STINKS! *gag*
Good luck!!!