How many instances of omxplayer are possible with 1xFHD and 2-3 smaller videos being played at same time?

Question

I'd like to have the following setup:

• Background video in seamless loop
• preload x videos and keep them paused or in memory until needed
• x dependent on videos in certain folder (create library)
• trigger video based on filename by a serial command (2x 1byte)
• keep background video running (FHD or 720p, depending on performance of pi 3 B+)
• play triggered video on top, should be played instantly or with very low delay

How could i achieve this the optimal way?

Greetings, Dom