Generally the super duper performance enhancements that some users claim to suddenly skyrocket the FPS in BnS by are Voodoo BS - or the improvements are so low that only plebs with a toaster PC may feel an actual improvement.
The solutions you tried are certainly not connected with your issue. DX12 wrapper, BNS buddy do little to absolutely nothing -- or even worse... A custom Nvidia profile may only benefit players with an Nvidia card that would normally belong into a museum... On your card, GPU settings for this joke engine are an absolute never mind (you may rather wonder how to improve the visual quality over default settings).
With your config things should be much better and they should be somewhat consistent - even you will still encounter FPS drops due to engine limitations they will be way less severe/they will only occur with much more characters and effects on screen.
Now it´s impossible to provide a satisfactory remote diagnosis like this but you can/should check a few things (and forget about the voodoo stuff):
-CHECK THOROUGHLY FOR THIRD PARTY PROGRAMS! And let go of the overzealous virus scanner, of the online cooperative office suite, of the ask.com search bar, of the whatever questionable things you may have running in the background.
-"Drivers checked"? Absolutely sure? Also: not always the latest NVidia driver is the best - new bugs may have been introduced (check Nvidia board/reddit). Especially with super duper "RTX enabled"...
-make sure you are not ping crippled - if you are waiting for server response this will also impact the fluency of your gameplay
-IDK but even on my OCed 9900k,1080 TI i (Windows 7) am not setting all full detail. Especially some of the Special Effects cripple the performance a lot (because of CPU limitations, it has nothing to do with GPU unless you are running museum hardware!). As a suggestion find my settings below, but experiment for yourself (effects for others set to 2 since this is the last setting that sill displays critical animations, for AA i am using ReShade). My FPS are somewhat okay to me which means normally not far below 60 and usually above 100.