Is there any problems using Nikon smallRAW file? I am using D810. Wil it effect final video size as I sometimes use Warp Stabalizer in Premier Pro?

You can use any type of raw files with LRTimelapse. Of course, if you render in higher resolutions than you capture your raw files, the videos will get scaled up.

On that note which is the best size to render for a 5D mk IV.?