mini-pcs have grown into attractive alternatives for raspis in light server/IOT roles. They don't have the GPIO functionality at which raspis excel, and they're relative power hogs, but they are also generally more expandable and powerful for server roles than pis, which are prized mostly for their low price, and (sort of) lower power consumption.
Not sure how good it will be running octo in a docker on a SFF pc - that'll depend on your processor and memory, but it's not wrong or insane to do it if it meets your needs.