In the off-chance this gets around to someone who could use this information,
from my own experience, trying to run Klonoa 2 on PS2 via OpenPS2Loader and internal HDD has sound issues where a small beep can be heard in the intro and nothing else, and in-game only the background music can be heard and no sound effects. There was a small instance where it ran fine, but I haven't been able to replicate that any other time. To fix this I put the iso on a USB flash drive and ran it from there. Been fine since then.
Posting cause I was struggling to find a solution for a while.
Also the remaster kinda stinks