Follow Ohm's law, of course
The thing is the Lavatube has a hard amperage limit, and it will not let you exceed a certain voltage for certain lower resistance cartos
without telling you. This is in a way good, because you can just put on it whatever you want and play, it will not break and the carto will not pop. It will just not increase the voltage. It's not that good because you'll wonder why the vape doesn't change as you keep dialing up the voltage. But now you won't. The problem is only a problem for dual coil cartos, because these need higher voltage to work well. So the only thing I'd avoid on the LT are dual coils.
Also be aware that cartos have various resistances, usually within 0.6 ohm of what is stated, but rarely way off. And that resistance actually changes as you use them.
I found that juices have different sweet spots, so take that into account - if a juice tastes great at 5 V on a 3 Ohm, another juice may need a lower or higher power to shine. But, I 3.0 Ohm Boges start getting awesome above 4.0 V, probably above 4.4 even...