I'll be going AMD next build no matter what, whether it's a mini PC or a desktop. I'm certain if I do make a new desktop it'll be the last time I ever do before pcs change completely. I think mini PC with external GPUs will be the future.
I've always liked the idea of an external GPU ...but those external GPU docks (usually thunderbolt?) are kind of hard to find, at least from reputable companies. They also have weird open air designs that I don't trust either ...or unusual power supply support. Please prove me around, because I would keep 1 just to support my extra/older GPUs over the years.