There's currently plenty of 3rd party VESA mounts for Mac Mini, I'm sure they'll have some for this new Mac Mini as well. They slide down into a "clamp" style bracket. They run about $15 on Amazon.
You can get 'sandwich' enclosures that put the mini between the monitor arm and the monitor itself, or off to the side. That's what I do with an M1 Mac Mini sitting next to me. Maybe it's a blessing in disguise since you can get these cheaper than what Apple would sell them for :)
Honestly, I wish they'd go with an external USB-C power brick.
The only reason they might not is that they want to keep everything across the entire line, and the highest end Mac Studio probably needs more power than USB can offer.
I bought a portable AC battery for my Mac mini for $65. Hard agree though that it would be a lot cooler if the conversion was in the cable so I could just do dc in.
The thing is, M chips run so efficiently that even with the power loss from conversion, it’s still pulling less power than a lot of PCs.
But yeah it running on a sleek dc battery would be a lot cooler
The Apple tech specs page says "Maximum continuous power: 155W" and USB-C PD supports up to 240 W these days, so technically it's doable, although it would be a nightmare with people trying to run it off the far more common lower power supplies (which it would have to reject because it doesn't have a battery to handle if someone suddenly plugs in some high-draw device)