Is there a way to have 2 wallets under the same OS and swap them in the client?
There is no way to swap them in the client. You could shut down the client, swap the files by hand, and then start the client back up. If you do that, be VERY careful that you don't accidentally delete, overwrite, or otherwise lose one of the wallets.
Do you just use the built in wallet encryption or use outside program like tryecrypt to encrypt it again?
I just use the built in encryption. That is good enough if the only thing you are trying to protect is your private keys. If you are trying to protect your privacy as well, you may want to consider additional encryption.
