Samsung bd1500 and a few ts muxer q's

Hi everyone.

I have had my blu ray burner and player about a week or 2 now and have made a few films and a few coasters!

All of the films i have have come as mkv files and i have put them through ts muxer to create a blu ray disc and then burned with image burn.

Some of the films have looked a bit grainy or snowy in the background even though they have been 1920x1080resolution,(300 fight club)? anyone else notice this?

Also when i put the mkv file through ts muxer i have to change the video resolution to 4.1 like i read you need to to get it working on a ps3, could this be down grading the quality?

i have put movies on verbatim bd discs and verbatim dual layer discs,do you get better quality the bigger the size mkv?

I just want the best quality and would love somebody to give me some help.
I have read through all stickys and posts , thanks in advance.