I had a lot of those cartons of creamed soup post-op, which I often added milk and unflavored protein powder to. I also used a lot of protein powder (both unflavored and sugar-free flavored varieties) and smooth greek yogurt. I bought oatmeal but discovered I could only stand the unsweetened stuff immediately post op, the normal stuff was WAYYYYY too sweet for me to tolerate. High protein milk (Fairlife in the USA, Natrel in Canada) was a great way to get in some more protein and a hundred or so more calories a day, as well as upping my fluids when water was weirdly awful to drink. I think I had some unsweetened applesauce, but not often.
Basically my rule for myself was if it wasn't a source of protein, I didn't eat it those first couple weeks. There was just so little room in my tummy or will to eat, I needed to make every single bite "count".
I think the biggest surprise was how much sweetened stuff in general disgusted me and tasted bad though. Pudding cups, popsicles, protein shakes, oatmeal... I had absolutely zero interest in sweet things. I lived off of savoury for at least a week before introducing limited amounts of sweeter foods. (AKA going from plain oatmeal to plain oatmeal with half a teaspoon of raspberry jam VS the high protein maple brown sugar oatmeal I'd been suggested to buy).
I know some surgeons include baby food in their post-op diet plans, but I can't imagine myself eating that post-op. If it's not specifically recommended for you, I would like to say it really isn't required. I was kind of emotional and crotchety after surgery and was even resentful of the pureed soups, so I can only imagine how crabby I'd have been to be eating food meant for a baby LOL. Your mileage may vary on that one.
I think my biggest piece of advice from one planner to another though... is DON'T OVERBUY. I was totally like "oh yeah I'm gonna stock up on all this stuff and it'll be perfect!" and then things I stocked up on... I ended up not wanting to eat and not liking. Stuff like said high protein oatmeal which I had always enjoyed before suddenly tasted terrible and now I was stuck with four stupid boxes of the stuff.
Buy enough for a few days so you're not stuck with stuff your new belly/tastebuds aren't digging. Yes it means you're a little less prepared for the post-surgery apocalypse, but there's always online shopping and grocery delivery if you don't have enough of something. Post bariatric surgery is the one time I'd actually advocate "better to need it and not have it than have it and not need it". Also, I really looked forward to grocery shopping post op because it was a great way to get out of the house and do some limited walking