Not all legacy’s are offered TTP. Also, it is offered to non-legacy as well.
There is no waitlist, spring admission sorta replaces that.
Viterbi Pathways and Trojan Transfer aren’t guaranteed transfer, but def a big boost and highly likely - you have to take correct classes and get the grades, then re-apply through common app again like any other transfer. But they know you are coming in thru these programs.
Biggest thing to consider is possibly giving up another 4 year, although you can attend a 4 year, but they discourage it cause they have to - they can’t encourage you to commit to another 4 year knowing you will leave it, other schools would frown on this. But kids do come into USC through these programs from a 4 year. Or do abroad or a community college.
Also housing for transfers is not that likely as a sophomore.
But if you really want your degree from USC it could be great for you.
This TTP thread is still current, program hasn’t changed: