You can buy and own an auto knife or butterfly knife, but you can't carry it without a CWFL. You can't own anything that actually shoots the blade out, where the blade physically separates from the handle.
There's no explicit restriction on blade length that I know of, just a mention of a "common pocketknife" not being a weapon, and the mention of items not specifically designed to be weapons. There's a lot of subjectivity there, so if you don't have your concealed carry license, I wouldn't take any risks by carrying anything that could be construed as a weapon and not a "common pocketknife".
A fixed-blade tanto would be very hard to argue as a "common pocketknife". But, if you have your CWFL and have some way of effectively carrying it concealed, have at it.