Full guides:
These guides could be updated and could have more info in the comments. Settings below is what I use.
Hover over red text for notes.
Origin → My Game Library → Right-click Apex Legends → Game Properties → Advanced Launch Options
+exec autoexec -refresh 120 -preload -threads 16 -forcenovsync -fullscreen -novid
Apex Installation Folder\cfg\autoexec.cfg
fps_max 121
cl_forcepreload 1
mat_copressedtextures 1
cl_ragdoll_collide 0
C:\Users\Your username\Saved Games\Respawn\Apex\local\videoconfig.txt
"VideoConfig" { "setting.cl_gib_allow" "0" "setting.cl_particle_fallback_base" "3" "setting.cl_particle_fallback_multiplier" "2" "setting.cl_ragdoll_maxcount" "0" "setting.cl_ragdoll_self_collision" "1" "setting.mat_depthfeather_enable" "0" "setting.mat_forceaniso" "1" "setting.mat_mip_linear" "0" "setting.stream_memory" "1509949" "setting.mat_picmip" "0" "setting.particle_cpu_level" "0" "setting.r_createmodeldecals" "0" "setting.r_decals" "0" "setting.r_lod_switch_scale" "0.350000" "setting.shadow_enable" "0" "setting.shadow_depth_dimen_min" "0" "setting.shadow_depth_upres_factor_max" "0" "setting.shadow_maxdynamic" "0" "setting.ssao_enabled" "0" "setting.ssao_downsample" "3" "setting.modeldecals_forceAllowed" "1" "setting.dvs_enable" "0" "setting.dvs_gpuframetime_min" "15000" "setting.dvs_gpuframetime_max" "16500" "setting.defaultres" "1920" "setting.defaultresheight" "1080" "setting.fullscreen" "1" "setting.nowindowborder" "0" "setting.volumetric_lighting" "0" "setting.mat_vsync_mode" "0" "setting.mat_backbuffer_count" "1" "setting.mat_antialias_mode" "0" "setting.csm_enabled" "1" "setting.csm_coverage" "1" "setting.csm_cascade_res" "512" "setting.fadeDistScale" "1.000000" "setting.dvs_supersample_enable" "0" "setting.gamma" "1.000000" "setting.configversion" "7" }
* r_lod_switch_scale - changes distance of LOD models/textures. 0.6 is default value. 0.0 gives most FPS but almost unplayable - unrecognizable pickups, some rocks aren't visible etc. 0.35 still gives somewhat noticeable switches between normal and LOD textures.