Try booting in Windows Safe Mode and see what happens.
Then boot normally, then ending/closing the processes for Opera GX, Discord, NZXT software, Steelseries software, other streaming software - and see what happens.
Memory use is of course a total sum of everything in that Processes column, so just go through that list and see what's using it. If the numbers in the column don't add up to the total used, then there's a hidden process sucking it all up - perhaps something malicious.