16" M1 Max here with TS3. I leave the TS3 plugged in and drive my external 4k monitor via HDMI. Works great, except I had an issue where it didn't recognize the the things attached to the TS3 after an overnight sleep. Unplug/replug fixed that.
This Mac is the most impressive Apple computer I've ever had, and I go back the the Apple II days!
I've been running for two days and haven't been able to get the fans to turn on. Under heavy load it gets a touch warmer than room temp. I suspect the 14" will have zero thermal issues...