Hi from Victoria Australia.
I buy on line and locally - fabric is expensive in Australia. Hancocks of Paducha and Fabric Depot have both been excellent suppliers to me for a long time now. You can mix fabrics from different manufacturers, sometimes to get the colours or the effect you want you will have to specially with your Art Quilts. Your machine may be the decision maker with which threads you use and poly has it's uses to be sure. No question is too silly because we have all at some stage asked it ourself and this is the family that gives the best support and encouragement for your quilting journey. Welcome Home.