Really depends on both the vape and user preference
We could give better advice on how to pack each different vape if you named them
No rule of thumb across the board for all vapes, they all work differently
I have convection and conduction that can be packed tight, light, full, partial loads depending on how you like it
Yet I have other conduction or convection vapes that are particular about how they are packed for best performance in relation to tightness, but they have to have a full bowl always to work at all
So we would need the name of the vapes in particular you want to know about before we could give more accurate advice
Personally I pack my vapes full most of the time regardless of their ability to do smaller bowls or not, and unless they are one that has to be packed lightly, I pack on the firmer side as I also prefer thicker and more dense clouds with a bigger hit at once
Some vapes have to be packed full to work, some can be packed as a half bowl if you like micro dosing (whatever that is lol)