Wearing regular socks under heated socks will definitely add extra insulation and comfort, especially if you are planning a full day of outdoor activities. However, with most heated socks, you may not need to wear regular socks underneath the heated ones.
The benefit of wearing regular socks under your heated socks is that you may not need to wash the heated ones as often. Keep in mind that if you do plan on wearing socks under heated socks, it may be a good idea to get the heated socks a size larger to accommodate the extra bulk or simply choose one-size-fits-all heated socks.