We did no clothes for three days and then commando in shorts for a couple weeks. It worked great. The training pants can feel a lot like a diaper so you may see differing results with that. I haven’t done them before.
We started late February and my son still doesn’t wear undies. I feel like they will just get in the way so I only put them on if he’s not wearing clothes in his booster seat but he’s peed in them twice so I feel like he still sees them as a diaper.
I do feel like mine dislikes the wetness in his training undies a bit more than he disliked being commando and just going on the floor. But if you’re just starting, I might still do the commando for a while because he won’t have to mess with trying to get his undies down before he goes on the potty and can just jump on by himself. Or experiment with both. I feel like you don’t have to fully commit to one way or the other.
I used underwear. It took a long time to get mines fully potty trained though but commando or underwear, he never cared if he was wet or not.
Get training undies they are padded