Bike saddle bag question

Went to a bike shop last weekend and saw a nice large bag that you can put under the saddle without using a frame. There’s a quick release system that goes with the seat post so you can put it on and off quickly. I was thinking of buying it for small 2-3 days road trip where I would stay in hotels and only carry some changing clothes. I would also use that bag for commuting since I would like that better than my back pack.

Anybody tried that? Does it work well? I dont remember what company was making them but are there some good or bad?

Thanks