I've found that this autoexec config (taken from: https://perpheads.com/threads/perpheads-performance-guide-2024.60890/) helps with fps quite nicely:
cl_burninggibs 1
cl_new_impact_effects 1
cl_threaded_bone_setup 1
fps_max 0
gmod_mcore_test 1
mat_picmip 10
mat_queue_mode 2
mat_specular 1...