Thats the grordbort weapons. They are famous for being poor in performance in even a normal game already. Dont use them ever in mvm except for maybe the phlog which if im right has the cheapest particles (being not heavier than normal fire).
And dont worry about those trees, mannworks has quite alot of them aswel. Its often better to use the same prop 50 times than to use 25 diffirent props performance wise. Those 50 are far easier to cache than those 25. Still be carefull that they arent going too far into the distance. Only a few rows should be enough for mvm. If you have an open view just add for example a clip in it to break the flat texture. Although even that isnt bad if you look at the skyboxes of the valve maps.
Still, fading distances could help on many of the smaller props. For trees i wouldnt recommend them due to them showing the flat area behind them. They are too visible. And if im right they already have good lods which makes them one of the easiest objects in optimizing.
Then i think i see a very long straigh path (its hard to see though how long exactly it is) but a too long straight path is going to make waves too easy. Especialy when its thin heavies can massively use piercing power and this can break balancing the wave as then 1 scout, 4 heavies and 1 engy are going to steamroll it. If you havent tested the map its better to do at least 1 test with a full team before you continue on detailing/balancing. If a path is too strong in mvm it breaks the fun because then its simply an endurance of how long you can defend that single path.
Another thing i see on your screens is that you use white light which is unrecommended due to looking unrealistic. Its best to have some yellow tint to it which normal lights also give. And many times spotlights already give enough reflections in light. It might be that they arent needed at all. but thats down to testing.
And many times in mvm a path only has 1 arrow inside it if its thin. See for example decoy and coaltown where the first few arrows dont have a left or right side. They only show that from the moment they split up. Just have the same arrow active for the rounds its needed to. This also allows you to center them in the path. Dont worry about them clipping with bots. Because on a round start they shouldnt be visible in the first place. This is because in many maps when bots reach the pit they are often free from the path restrictions. Only in mannworks that isnt which is why airblasting is extremely effective there.
Make for example 4 groups of arrows in a naming style like: start, left, center, right. Start is allways active while left center and right are only for specific rounds. The only reason why in my map that isnt done is because the side of the rocks is also decided and for defensive reasons its actualy needed to have that info (otherwise people will guess that the bomber will take a side randomly). And in my map there are 7 groups (start, early left, early right, flank left, left, right, flank right).
