Do my other devices keep drawing power when the rig is off?

Yes, and it is worth knowing about. Many electronics draw a small standby or phantom load even when switched off or idle - monitors, chargers, the PC's own standby circuit, and networking gear all sip a few watts continuously. For a mining setup, the relevant figure is the rig's idle draw, which can be 60-100W on a desktop just sitting at the Windows desktop. That idle power earns no MLRT, so it is pure waste during hours you are not actively mining. Measuring the off and idle draw with a smart plug shows you exactly how much; if it is significant, scheduling deep sleep or a full shutdown between mining sessions removes it entirely.