You got answered on r/mikrotik ?

Mailcow.email

Mailinabox

https://www.serverrack24.com/10-inch-12u-server-rack-with-glass-door-312x310x618mm-wxdxh.html

I don't have USA links sorry but that's the general gist

10" racks

Consolidate power might not be possible 12v? Even 20amps is 4-6 computers. Just get 10" pdu's they have 3 plugs. I know there's 17 computers and 3 switches that's like 7 pdu's..

20 shelves

2x 10u 10" racks..

You'll need to have a 10u empty to keep going for expandability.