Version 2.22 is out: minor bug fix of a runaway dialog when unknown block types were encountered. Worth fixing so that the new beta won't cause this problem for users. That said, the upcoming 1.5 version has a new texture structure, which Mineways will blithely ignore. Mineways will still work, but won't support the new block types until I find the time to update the program.
I know we can use any amount of blocks, but I want to know how big each of those blocks can be before losing texture. We have the option in the program to set the size of the blocks. That would make each individual block bigger, which would also stretch the blocks texture. Is there a known block size for best quality? Or does that still not affect the texture?
Blocks shouldn't lose texture ever. Larger blocks will show more detail. Blocks that are 2 mm (the default) show a bit of texture - I can read "TNT" on those blocks, for example. However, I find that 3 mm blocks make more of the textures recognizable.
Cost is based mostly on how much material you use. Smaller is cuter and cooler and cheaper. The main limitation on making models small is wall thickness: thin walls may cause your model to be rejected, as the print service will fear that the model will break.
Griefers on Minecraft don't usually tend to kill. Rather, they tend to destroy property, at least from what I've seen, usually by setting structures aflame. Still, griefers have subcategories, and I'm just naming one.