Welcome Greg! Gee, there are as many opinions on these topics as there are choices! If you search the old messages here, you will find a number of conversations about all these topics. Personally, I do find there are differences in thread. Superior Threads makes some sweet stuff and their website can provide you with an enormous amount of info on thread... I do love Alex Anderson's thread line but it is pricey. That said, even though it may seem insignificant, consider (and another reason to be precise in cutting fabric) even 1/64 of an inch, over say 30 seams is nearly half an inch difference. And in quilting, half an inch is major.
When you ask cotton vs polyester, do you mean fabric? I prefer the name brands and I love batiks. If I am going to put hours and hours of work into a quilt, I want it to last. And I find the better fabrics have prettier designs. Just me though.
Hope you get more info to help you wade through all your choices! We are looking forward toseeing pictures of you projects.
Ellen