Best type of tire for bikepacking
Tubulars would be a bad idea, because you need to glue new ones on and most shops don't handle tubulars so getting spare parts when necessary is hard.

Most people will run a standard clincher for touring on roads, since there isn't much benefit for running a tubeless system for riding on the road and most wheels for road bikes are not tubeless ready (especially for high spoke strong wheels you'd fit on a touring bike). Everyone knows how to handle tubes and the tubes+tires are available almost everywhere if you choose an appropriate wheel size (you'll be able to find 26" wheels almost everywhere, 700c many places, 650b less so in the US, for example).

If you want to run tubeless, you can (which would be a preferable starting point for off road touring) since you can always throw a tube in a tire or put a tube+new tire on if necessary (if you find a shop, note that it might not be equipped for tubeless). Note that you are carrying some extra kit with tubeless such as an extra valve, sealant, less tubes than you would carry with a tube system, plugs, and what not versus say a patch kit, some boots, some tubes.