2GB runs fine for a simple playback client device. If you want to run a load of container/server services in the background then 4GB or perhaps 8GB will be more suitable.
So all seems fine
Except the 4k video that stutters.
Might actually be the 2GB version that is too low specced?
Idea: RPi 5 with 8GB (~85€) - Raspberry Pi M.2 HAT+ (~15€) - some old NVMe SSD I find in the office cabinet...
Should give much better performance disk-wise and maybe also helps with the issue of the 4K decoding?