You can do all this with notepad. In notepad, press ctrl + f to quickly find these settings.

1. Go to C:\Users\username\AppData\Roaming\Arrowhead\Helldivers2
   
2. Open user_settings.config
   
3. Set particles_cast_shadows to false (it is already disabled for some machines).
   
4. Set particles_receive_shadows to false
   
5. Set particles_local_lighting to false
   
6. Set particles_tesselation to false

Next

1. Go to C:\Program Files (x86)\Steam\steamapps\common\Helldivers 2\data
   
2. Open settings.ini
   
3. Change memory_size = 26214400 to 78643200
   
4. Change num_refills_in_voice = 2 to 4

then you're done! Me and others who have tried it have noticed no visual downgrade.
I'll add the nerd ♥♥♥♥ details later if I'm not lazy
p.s. what the hell is with all that preamble that these guides have? this isn't ♥♥♥♥♥♥♥ google, there's no SEO. anyways happy diving.