Regarding MinePeon with USB miners:
Is there any limit of USB devices that it will auto-detect (other than the 127 standard USB limit)?
When removing or adding new USB miners do you need to do anything over than reboot? (ie will it automatically detect that devices were added or removed and start using all available devices)
There is the unconfirmed limit of approx. 50 USB Miners which the RPi can handle.
When removing or adding USB miners you don't need to do anything. Insert one at a time, cgminer will autodetect it.
But for removal, well you could just pull them out but hot-plugging here really means HOT plugging. So don't do it, stop cgminer first in the console with
"sudo systemctl stop cgminer.service"
Wait a minute.
.
.
.
.
Remove the USB Miner
.
.
then
"sudo systemctl start cgminer.service"
Done.