Pen tablets stay at ambient room temperature. They do not get hot or even warm.
If your pen tablet or its cabling gets noticeably warm or hot. Disconnect it and contact support immediately.
Pen displays either stay at room temperature or get very slightly warm - maybe close to human body temperature.
You may find that the amount of heat is correlated to the brightness setting.
You may find that the heat is localized in certain regions on the tablet. This is normal for pen displays.
If your pen display or its cabling gets very warm or hot. Disconnect it and contact support immediately.
These are essentially laptops. So they in theory can get warmer than pen tablets and pen displays which is normal for laptops. But your experience may vary depending on what you are doing.