If you need room for expansion, then just run a bare minimum of coolant visible in the header. It does not need to be full ! Just run enough so that when cold, you can visually see there is coolant in it so you always have that reference.

I just use an Audi/VW header tank on mine and have zero issues

And if concerned about HG or something, always monitor/log pressure in the cooling system

And an overflow bottle serves the additional purpose of allowing it to eject water, and then if correct cap is used, draw it back in again as it cools. Although I prefer to keep the system running as a closed system without the need to eject and draw back in.