First of all, it should be clear that underwear is what we often call autumn clothes. There is no absolute answer whether to wear underwear inside thermal underwear. It depends on the material of thermal underwear. If the material of thermal underwear is silk, space cotton and so on, this kind of thermal underwear can be worn and it is more comfortable to wear. But if the thermal underwear is made of acrylic and polyester, it is not recommended to wear it. It is best to wear an underwear inside, and then wear thermal underwear, so as to avoid the thermal underwear rubbing against the skin, otherwise it will lead to an increase in dandruff and dry and itchy skin.
Wear a warm vest when wearing underwear. If you wear a vest directly, your arms will get cold. It is best to wear tight underwear inside, and then wear a warm vest, which can also bring better warmth.
Of course, the above is for reference only, and you can wear it according to your actual preferences.