1 - To see textures fast write: /dl [user] , then go to multiplayer, they upload almost instantly with 3.8, dunno if its for Mac.
2 - To make transparency, create a new canvas, but a ransparent backround one (at leasts works for me) and draw, type, or whatever in it, abioslu, leaving some space for transpearency.
3- Im not precise, but it increases your texture quality , at least thats what i "heared"