The only volt drop off I've noticed comes from the weakening charge of the battery. You are using the battery directly ergo it'll drop of as used. To me that seems pretty consistent.
"If I use the charged battery then it drains energy from it, and will drop off accordingly."
Not ever noticed a mech to have
fluctuating drop offs beyond what isn't due to me vaping hard one day, light one day, ... the charge drops according to my use. Eventually there's the big "drop off" where I go to vape and hitting the fire button results in sucking juice but no vapor. About then I get the notion it might be wise to swap out for a freshly charged battery & recharge the one I was using in the mod. *chuckles & grins* And by freshly charged battery/ies I mean ones that are charged but have sat in waiting for at least a day, allowing them proper resting state.
I'm glad you like regulated mods though. I am genuinely happy for and with you that you found what suits you.
This leaves more affordable mech mods for me to use.
I like paying $50 or under for a mod as I don't see any value to fashion, which ultimately I think is what the hub bub is about in all the new fangled and assorted coloured regulated mods is about. Sorry, I got no need to keep up with the Jones' or Smith's. They don't define me, I define me.
This is not to say I do not understand the argument of safety which a regulated mod might offer. I do and I willing accept the added responsibility needed to use mech mods. Sure there's a risk involved. there's a risk involved with me stepping outside my flat door, out by the stoop is the sidewalk. There's parking spaces just after that. What if some car came careening over the sidewalk and body checked me? Honestly, shit happens and we can only do our best to get on with it, nay? *chuckles*
Or worst case scenario, I wake one morn and come to realize we all no longer exist as we've been gobbled up by a black hole. Ever contemplate the statistics on that probability? I had to stop as it began giving me a fright. So, I said fuck it, if a black hole wants to eat us there's nothing we can do to stop it, if it happens there's nothing I'll feel about it anyway as it'll be done with or without my knowledge. I've a bit of belief that black holes are our Universe's way of playing Shiva, creator and destroyer. I think then based on that belief if we're destroyed it'll be to make us anew somewhere else. Of course, that's merely my opinion and I realize that.