You might try making a few blocks yourself and see which you like best. I made a wall hanging with string blocks and used no foundation with the first block. I was amazed at the amount of stretch there was when sewing those blocks together. That project ended up all right, but I thought I'd try another project using a muslin base. It was definitely heavier, but I didn't need to be careful at all about stretching when sewing the blocks together. I then tried making blocks with paper meant for that purpose. The papers came off fairly easily, but were expensive. Then I discovered I had an old phonebook, so I tried blocks with that. That paper came off really easily and was free. I found it helped to fold the paper along the seam line to help it tear away more easily.