I keep everything standard. I have some sites with over 100,000 hd, 1080p, and 4k videos. I use .mp4 with h.264 and CRF 23 in ffmpeg. I use 24 bit / 192 kHz for audio. For small files I would just keep it at CRF 25, 16 bit / 44.1 kHz. I never change the -r in ffmpeg because it messes up the frame rate.