Files are saved on SDD
CPU usage during stress test doesn’t go above 15%
Little remark:
Don’t think it’s “fair” to state that performance is not OK or under par.
I can run Obsidian on a Raspberry Pi and state here that performance is not OK.
Disk IO is a burden on stress tests.
Guess your not doing your tests on a 386-machine 
so CPU should be rather OK.