Cool thing about RA so many options! But sometimes too many options 
That’s a decent machine it should handle it well but here’s some suggestions…
Set audio resampling quality to lowest, or just disable audio syncing (note if you disable audio sync and also disable Vsync the framerate will be unlimited). Set 128ms audio latency. If that works you can later lower it to 64ms or 48ms, or even 32ms or lower on some systems. To begin with you can even disable audio completely in the menu for testing purpose to really isolate the problem to audio and check the framerate…
Try changing audio resampling to Nearest from Sinc, it’s a faster basic method of resampling. If using Nearest I’d also suggest try changing audio output rate to 192000 or 96000, from the default 48000 (show advanced settings must be on or this option is hidden). Higher output rate should give higher quality without any significant performance hit if the soundcard supports the rate. Especially with simple Nearest resampling a higher rate should help give smoother sound. In the config file it’s called “audio_out_rate”. If the soundcard does not support the rate it should be automatically reset to default 48 kHz.
Other than that Enable threaded video. Disable any shaders. Disable Runahead. Set frame delay to 0ms (this gives the computer the most time possible to work on each frame). Try Vulkan video driver if possible. That’s all from the top of my head might be something else but I’d start with those…
Oh and when you’re not sure of what you’ve done you can simply hit the start button on the controller in the menu, that resets the option to the default value!
That’s a decent machine it should handle it well but here’s some suggestions…