Well, what I do is make sure that all stems are more or less equal to each other volume wise. This not only counts for stems within one song but also try to level each and every songs to the same volume.
This means everything is kind of balanced which makes FOH mixing a lot easier, because only small adjustments have to be made, without anything being way too quiet or, even worse, too loud.
I always make sure that each stem will not exceed around -18dBFS so you you keep enough headroom and will stay within the ‘green’ area of the LP16.
And yes, the more separate stems you have the more you give out of hand to the FOH engineer. If it’s a good one your blessed, otherwise it may get dirty.
Feel free to E-mail me if you have more questions (firstname.lastname@example.org)