Hello,
TF2 runs so bad and it desperately needs an engine update.
I have Ryzen 7 2700x It's really high end cpu but still with Mastercomfig High preset I get 165+fps while nothing happening, drops to 90 fps when fighting. I have a 165hz monitor so it's really noticeable. 

If you want to enjoy tf2 without lags definitely use mastercomfig. Using a simpler hud will also help with fps. Use process lasso to make tf2 run on only real cores.

My launch options:-dxlevel 98 -no_texture_stream -novid -nojoy -nosteamcontroller -nohltv -precachefontchars (delete dxlevel 98 after the first launch. Dxlevel 98 gives some of the particle rendering to gpu. If you want the most fps use dxlevel 81 but it breaks a lot of the stuff.)
Autoexec.cfg:
//Quick resupply
bind downarrow "load_itempreset 0;"
bind leftarrow "load_itempreset 1;"
bind uparrow "load_itempreset 2;"
bind rightarrow "load_itempreset 3;"
mat_queue_mode "2" // 2 makes the game multi-threaded
mat_vsync "1" // vsync. Enabling it should make game feel more smoother. If your monitor is below 75hz make it 0
r_threaded_particles "1" 
r_threaded_renderables "1" 
//cl_threaded_bone_setup "1" //  You need to try these on your own because some of them
//cl_interp_threadmodeticks "1" // makes the game crash/bug/glitch depending on the hardware.
//cl_threaded_client_leaf_system "1"  //  Remove the slashes at the line beginning.
//r_threaded_client_shadow_manager "1"  //
//r_queued_decals "1" //
//r_queued_post_processing "1"  // For me r_queued_post_processing made it all buggy.
cl_mute_all_comms 0 // Makes sure you see your own text messages. A bug with mastercomfig?
//tf_use_match_hud 0 // Disables the hud on top of the screen. Actually makes the game run faster when cpu is the bottleneck. But It's kinda usefull so choice is yours.
//cl_hud_playerclass_use_playermodel 0 // Disables 3d playermodel on the bottomleft. Should improve fps depending on hardware.

These should make the game run better somewhat. I can't imagine playing tf2 without them. There are multiple reasons why tf2 runs bad. But it's mainly because It's not optimized for multicore systems and high refresh gaming. Tf2 was made when pc's had 2 core 4 thread and monitors were 60hz. Tf2 uses only 3 cores at best. So forcing multi threading on a game that wasn't made with multi threading on mind doesn't make it run super well, maybe only slightly. Even when It's using those 3 cores, it's very unefficient at it. It's similiar to Crysis.

How well does your game run ? Enter the poll, write a comment and thanks. Cya