Zetsubo
I'm sorry but I have to correct yttrium a bit.
yttrium-high increases TF2's thread priority, which should really not be an issue unless you've got a shitload of other applications open
-high improves responsiveness with better preemption and execution of tasks. It helps even with just background processes. However, these benefits depend on the CPU.
yttrium-nojoy is really only useful if your game keeps enabling the gamepad and disabling mouse/keyboard (happens for some people), but apparently it doesn't even work anymore so YMMV
It saves a bit of memory and decreases startup time by preventing the joystick system from starting. It still works, you can check this by comparing the stdout output from TF2 when -nojoy is present and removed.
yttrium-threads forces TF2 to use a certain number of threads, this is very likely useless for you as TF2 automatically handles thread creation
No, this tells TF2 how many worker threads are available for tasks. TF2's automatic detection for worker thread count is limited to 3 threads, so -threads allows you to force a higher count.
yttrium-useforcedmparms -noforcemaccel -noforcemspd became irrelevant in 2011 when raw input was added
But some people have problems with raw input, so it is still useful for those with raw input disabled.