If I turn over a follower to the blades, can I still use them?

If so, where will they be found? In the cave, or at their original locations, or somewhere else?

After you part with them, they stay in the temple so they can be found and re-recruited any time after that.

I found my housecarl follower in my house with blades equipment on lol

You can still have your followers follow you, I had Mojll the Lioness follow me after I had her joined the blades, when I left and came back with her another time her and Delphine started sparring... I thought at first it was an actual fight and almost jumped in, but there were no red dots...