I was making some mods on my Freeplay GBA and homebreed Recalbox version that I have the picture at the same moment on the Waveshare display and on TV over hdmi. My config,txt looked like this :
hdmi_drive=1 #Normal DVI mode (No sound) (2 for HDMI with sound)
It is now commented as I used after the basic lcd driver from Waveshare the fbcp-ili9341 driver that you must compile by yourself but that has alot of advantages as it is much more speed as conventional drivers. Not only you have the possibility to compress/expand/repositon the screen but also this driver only write the changed part to the screen memory and not all the time the full frame. You see it very good with games like Quake.