I’ve noticed that many of the proponents of foundationless frames are using medium brood boxes- not deeps. The instruction about inspecting foundationless frames tends to be focused on maintaining them plumb as you rotate - but new beekeepers with deep equipment should also recognize that there will be a big difference in weight due to the added volume of a deep frame, compared to a medium.
The critical moment is at that first inspection, with several factors contributing to the chance of losing hunks of comb, even if you’re trying to be careful: soft, new comb filled with syrup, nearly filling a deep frame but not adhered on sides or bottom, means it could easily detach from the top bar with any movement, before it’s even lifted out.
What’s done is done with my first brood box, a deep with unreinforced, foundationless frames. I learned the above lesson & have decided to add 2 more mediums instead of a second deep box (for overwintering in my area). If I were to start over I would use all mediums.
My bees started out with nice straight combs, but after my screwup their subsequent combs were crossed. So, another thing I’d do over is go ahead & use plastic foundation. There is small-cell foundation available & I agree with @Gerald_Nickel, no point in fussing about a bit more plastic when you are using the Flow super anyway
I’d still stay away from wax foundation because of the traces of chemicals in it. And, as @Dawn_SD has said elsewhere on this forum, you can switch out over time to convert to all-foundationless if that’s important to you, and more likely be able to avoid cross combing in the process.