LambdaCoreI recommend putting in the following launch commands:
-threads 4 -novid -heapsize 4194304 -mat_dxlevel 98 -noforcemaccel -noforcemparms -noforcemspd
These helped me a lot. If these don't work I guess you'd probably just wanna wait till the TF team finally gets around to optimizing the game.
I have similar specs and run other games perfectly; so unless you have problems with other games don't go messing around trying to fix your computer when it isn't broken.
-noforcemaccel -noforcemparms -noforcemspd stopped working years ago. these are placebo
-mat_dxlevel 98 is usually the worst dxlevel for fps. 90 or 95 better if you want to use dx9, but for fps 81 is best
Pretty sure -threads doesn't matter depending on specs
don't remember what -heapsize does exactly but I doubt it's a significant difference if you have it in launch options. Graphics configs probably already put it at recommended values for fps