If you currently have a regular drop bar brake lever, then you can use that at the end. If you mount it with the lever pointing back and it has aero cable routing, then it can be a bit awkward looking. Some people will mount the lever backward, with the lever pointing forward, which I've tried and it felt weird to me.

You won't be able to use a bullhorn/TT lever at the end because it requires a short straight section, which your bars won't have.

A cross/interrupter lever near the stem will work fine.

Personally, I messed with a couple flop-and-chops and various brakes. Eventually, I went with a proper bullhorn bars and TT lever, which has been much better.