I have some shelly devices in use and had no issues so far. A Shelly EM, two led strip controllers, a dimmer and some shelly plugs. Not heavy loads in any of them, I use them way below their max load specs.
I think it depends on your particular use case, if it's just the power monitor I don't think it's going to overheat, problems probably come when the relay they include is handling a heavy load for a long time. I think their rate for max relay load is too optimistic, but apart from that I'll say their producs work nice and are easy to set up.