I had doubts about the gameplay since you jumped into detailing so quickly without testing a public alpha, but after running around the map, the gameplay looks very playable. There are at least 3 paths to every point that all are valid choices of using. So congrats on not screwing up the most important part! I also really like the dynamic element choice you've included. After every cap the cart stalls, allowing red to regroup and preventing steamrolls from point to point. nice!
before you get this on servers, do a nice solid gameplay pass of clipping edges, clipping all your stairs, removing collision on props that get in the way/add clipping around them (like pipes on the wall you can get caught on), lighting all your dark areas, adding plenty of arrows, adding fade distance to A LOT of the props, and better optimization in some key areas.
First of all I would highly recommend getting rid of
ALL the smoke. Aesthetically, it's great. It's eerie, and compliments your swamp vibe perfectly... but it is a big FPS killer and will be very apparent when you have 24 people playing at once. Consider that the FIRST thing to get rid of when you start getting complaints about lag.
Here's some other things I saw:
Here's the first area that had bad FPS.
Not sure exactly where to put the topmost hint/skip, since the building is "open" all the way to the peak of the roof... maybe someone else knows.
This area had the worst FPS in the map. Lots of smoke all around, and tons of props+water rendered from all directions.
Occulders may be your solution for rendering all the swamp props past the left. I think a lot of your map could benefit from occluders.