Choppiness issue

You should try out area portals, occluders and other forms of optimisation. If you turn on mat_wireframe 1 ingame, you can usually tell what the culprits are.

EDIT: By this, i mean... if you can see something through a wall that you shouldn't be seeing, then it's not optimised properly

Your problem is a magical creature known as optimization, is nubcake mentioned. It can be the most difficult thing ever if you don't design your map with it in mind, but if you build it AROUND optimization techniques, it'll do wonders for you.

View http://forums.tf2maps.net/showpost.php?p=6378&postcount=3 and scroll down to Optimization Guides / Techniques. These are ALL required readings, I know it's a lot but trust me when I say it will help you in the long run. A map is a waste if it plays choppy.

AFTER you have done some reading, if you need some clarification then post back and let us know, don't feel you need to 'get it' all in one go . It's a lot to take in, so take it slow.
And good luck!

A quick tip though: Start by doing all of your brushwork in the NODRAW texture (search nodraw or tools in the texture browser). Only texture brushes that will be seen by players in-game.

nubcake said:

You should try out area portals, occluders and other forms of optimisation. If you turn on mat_wireframe 1 ingame, you can usually tell what the culprits are.

Click to expand...

Occulders aren't that useful, they are hard to calculate for the engine, and can make things worse if not used properly.
I'd suggest using hints instead

you select the brush, and apply the nodraw texture to it, then you open the texture tool, your cursor should change, now crtl+click on all the sides you want to texture, and apply the texture you want.

Yeah this is basically how it works:
If you SELECT the brush with the Select tool first, THEN use the Texture tool (SHIFT+A shortcut), it will texture the entire brush.

Instead, deselect everything, THEN open the Texture tool, then start texturing.
And a quick way to use the T tool, instead of selecting a face and clicking apply, simply select the texture you want, then right click on the face you want to texture.

So remember, left click SELECTs, right click TEXTURES. Also, if you want to texture something with a texture you already used, in the T tool you can SELECT (remember that left click) the brushface with that desired texture to select that texture, then right click a different face to texture it.

Sorry if that is confusing, I promise it makes sense lol.