I think you are right. There are a few testnets out there and if they can get the votes then they will become the mainnet but that is super weird at the sometime because we could have these competing organzations jockeying for position to be the mainnet. It's confusing. As far as a voting UI I saw this.

Don't trust it though yet. I can't say if it is legit or not.

http://eosportal.io/

Update: Also one of the testnets running is the Jungle EOS Network

If you look at the top of the page you can create accounts up there and then go to the faucet and get some EOS and Jungle coins on the Testnet.

When you create the account it ask for the Owner and active Key. You could just use the public key from this set for both because it doesn't create a pair in their automatically.

Private key: 5Jxq8mPBjMoKnW1xpXJudW3bssPHXpuhCynAq1tvaPKwf9hddGD
Public key: EOS596LUkD5Dwz3tkRQUJvCs2sXySxoEek2gjza2x69rjmdz497GA

But my impression is that once users vote on one of these testnets and get 15% votes then the mainnet will launch with those Block producers as the main ones but all usernames and obviously account values will be wiped out.

I hope this helps