I suggest you mix your nic base to 50mg/ml at 50/50 pg/vg.
In other words add VG to cut your 100 mg PG nic solution with an equal amount of VG and you'll end up at 50mg/ml close enough to a 50/50 pg/vg base to use for making your
e-liquids in whatever strength you wish.
You could do the 24mg for your base nic if you feel like its your preference, but imho, in any event I would
NOT mix it down as
straight pg nic, but rather as 50pg/50vg. Otherwise you will be stuck with some recipes that cant possibly be mixed to higher vg final ratios than the 70/30 you're currently happy with. If for example at some point you want a nice high vg
juice for use in a dripper,
you'll be shiz outta luck. ie: no joy.
In fact, if you were to start a 10ml bottle of
juice with a target nic of 18mg using a 24mg PG nic base and add just 10% flavorings youll be hard pressed to get anywhere near even the 70/30 target ratio youre shooting for. More like stuck at 85pg/15vg because you'd only have enough room left in the bottle for 1.5 ml of VG after you add the nic and flavorings on the 10% flavor bottle of juice.
hth