i did a lot of research on ways to boost performance with launch options recently and i found some obscure ways to, which don't have many results when i looked them up and i thought it would be a good idea to help spread the word about 'em. if i find any more i'll try to update you guys. thank you to turbochad69 for his help [list]
[*] -r_emulate_gl: it emulates openGL only on windows. should give a performance boost for most GPUs; be sure to test it out with a benchmark before you use it. unfortunately not many people know about this launch option and only know about -gl
[*] -softparticlesdefaultoff:disables feathering when rendering particles.
[*] -limitvsconst: limits the max amount of vertex shaders, with the max value being 256.
[*] -noqueuedpacketthread: disables thread creation when sending packets of larges sizes. NB - only works on linux.
[*] -noff: launch option to disable force feedback on controllers. gives a tiny performance boost
[*] -gl_texclientstorage: utilises GPU memory to decrease memory usage. only works on macs. MAY CRASH THE GAME ON OSX IF YOU HAVE BATCHED TEXTURE CREATES AND DESTROYS ENABLED
[*] -soft: enables the source engine's software hardware rendering mode. may give a performance boost depending on your specs
edit: i bit off MUCH more than i could chew with this