First of all, congrats on your new bun!
I adopted my English angora when she was already full grown so I don’t know about baby bunny vs adult wool. I try and brush my girl every day and she always has a few matts around her bum and hind quarters. She used to have really bad ones behind her ears and I would have to brush her twice a day there to keep them from getting out of control, but it’s been months since that’s happened. Maybe it’s because it’s warmer? Or it could be her new bunny friend is grooming her there.
They’re just a very high maintenance bun. The matts won’t hurt him if you’re getting them right away. The main concern is hot spots and creating skin irritation which won’t happen if the matt is broken up right away. You could try trimming his wool until he’s grown, just be very careful with scissors as their skin is quite thin.
And just in case whoever you got your bun from didn’t mention it, angora’s should be given papaya enzyme supplements once a week to prevent wool block. The amount will depend on your bun’s size (my 6.6lb gets 2 tablets every week) and before giving it to a baby bun, I would check with your vet.
In short, you’re always going to be constantly brushing him, but if it’s only once or twice a week, he’ll be fine.