I’m not an expert, but I do have over 400 trees in 5’ tubes since 2023, so here are some of the things I’ve experienced and learned:
Most of mine had a single leader when I planted them with the tubes, and often that main leader will grow up and out without side branches.
Sometimes they form branches in the tube, and usually they will fizzle out as they have nowhere to grow/get stuck/shaded out. You can optionally pinch competing new growth off except for the leader you want.
This year, I had a late spring frost, which resulted in lots of side branching inside the tubes, but a main leader still took dominance and grew out of the tubes. I’ll remove the tubes this winter and trim anything back inside the tubes, and remove leaves.
For your trees, I would probably try pruning any large/vigorous competing leaders, but not worry too much about small/thin/weak side branches.
I recommend some bird netting on top of the tubes, bluebirds and others tend to fall inside and die if you don’t
Use stout, rot-resistant stakes. 1"x3/4" wood stakes (pine, red oak) rotted out in 1.5 years at my house. I used 1/2" rebar at the orchard and it’s been great, especially if you have rocky ground. Be sure to pound them in deep enough - think ahead to when you have a tall tree and all that wind load pulling on them.
Tubes are definitely not maintenance free, plan to be checking on them regularly and having the tubes off once or twice a year. Still, I can’t imagine doing a large number of trees with cages (time, cost). Even for a fenced in setup, I would still use tubes - I think tubes promote vertical growth, so you don’t waste years trimming low branches off of short trees, wasting the tree’s energy.
These chestnuts were planted ~July 1st 2023 as ~2 foot tall seedlings. Tubes are 5 foot tall, many trees are about 10 feet tall now. I have found the need to add bamboo stakes to many, as they were too tall for their trunk diameters. Hopefully that resolves next summer as they bush out and thicken their trunks up. You can see the green filling up the tubes in the photo - that’s leaves and/or side branches. No big deal, I’ll be removing tubes this winter to trim those off.
I used 3/4" schedule 40 pvc pipe. It’s weather resistant and allows the tubes/trees to move to some extent. I would probably trim off side branches. The tubes scrunch all the leaves and branches together and they don’t get full sunlight to each leaf. Be sure to water during hot and dry periods. Without adequate holes for ventilation, the trees can bake.