Run your performance monitor (Ctrl-Shift-Esc) and watch for spikes on your primary drive. I'm having a similar issue, no FPS drops but inventory and NPC's won't load, until my SSD usage drops back down from 100%.

The problem with the NPCs not loading correctly/not showing may have to do with your internet. I don’t know if it’s constantly happening to you but if so, try going to a different area, ie going to the hanger, and coming back to the main area can fix that issue. Regarding tour FPS problem, I heard that going into the task manager and having the game connect to 2, 4, 6 cores of the cpu may fix it, I’m not quite sure if that solution is the solution to your problem though.