Every program is different. Check with your team. In my program, I didn't do a 2 week pre-op mostly liquid diet. Instead, I was on 800-1000 calories very low fat high protein for the two weeks prior to surgery with 60 grams of protein at day. I started using shakes well before surgery for breakfast and now, almost 9 month post-op, I probably have a shake for breakfast 4 days a week.
I think as you get to post-op, after the liquid diet (I was allowed protein drinks immediate after surgery), I alternated between using protein powder and liquid protein.
This morning is 10 ounces of coconut milk, 1 scoop of vanilla protein powder and a handful of frozen tropic fruit in the blender. That will hold me easily until lunch - about 230 calories and 25 g protein. If I want to beef it up, I'll use Fairlife Skim Milk for another 13g of protein.
You may find post-surgery that the taste or texture of the pre-made drinks may be an issue, so don't stock up too much, You're tastebuds change in those first few weeks after surgery.