Poor performance despite low CPU and GPU utilization

i5-2400, GTX 1050, 8gb RAM, windows 7. I know I shouldn't expect much from this rig but both Ninja Gaiden Sigma and Dragon Quest Builders: Alefgard o Fukkatsu Niseyo perform pretty bad without maxing out my CPU nor GPU. CPU load seems to never really break ~60%, GPU stays at 30-50% but both games drop down to 40fps sometimes without increasing the GPU nor CPU load. I played around with a lot of the settings including the renderer, some of the debug options like SPURS threads, SPU threads and block size without any effect whatsoever, except for Multithreaded RSX - it increases the CPU utilization but doesn't improve the framerate whatsoever, just introduces stutter from 100% load spikes. Temperatures are fine so it's not a throttling problem. It seems to be a specific problem only with some games since Skate 3, while running like ass, did peg my CPU at ~100% at all times. So what gives? Is there anything whatsoever I can do to "force" RPCS3 to use more resources?

EDIT: After some more playing and testing Ninja Gaiden Sigma seems to be particularly effected by any fire effects and black spider clan enemies first encountered in chapter 4 - both slow the game down to ~40fps. Dragon Quest Builders seems to be straight-up bugged though - as long as you don't move it keeps perfect 60fps, as soon as you move - no matter what the camera is pointed at and what's rendered - it drops to 35-40fps until you stop at which point it shoots up back to 60. Hilariously enough moving around while jumping keeps the fps at steady 60. Again, both games don't even try to make use of more of my system's resources in those instances and no settings seem to fix it so what the hell could be going on here? I've tested some other games as well and they're performing as expected - either very well with low cpu\gpu utilization or very poorly with 99% cpu usage, but Ninja Gaiden and DQB are a total mystery.