Since you're talking removeable battery, you're talking mods. You can either go VV, VV/VW, or mechanical. Or put something like a Kick in a mechanical to get VW. A huge variety to investigate
In the tube mods the SVD, Vamo are good units. But jump down and do some reading the VV thread:
Variable Voltage APV Discussion
You'll also need at least two batteries, more is better, and a good charger. Don't skimp on any of those items. Something that runs 18650's, you can easily get good 2900 mA ones.
Or, get two (you said!) MVP2 units. But they're not replaceable, but are 2600 mAh rated, and are very well made.
Yes, 200 - 250 or so charge cycles is the usual rating. Probably the lower end chain vaping, as that would put extra stress on them.
Might just need to add extra flavoring to your mix?
Any hardware failure can cascade, and damage other parts. Or do you mean that the adjustment knob was so loose the setting changed in your pocket and you didn't realize it until vaping? The SVD has a pushbutton method to lock the current settings - vv or vw mode, and the setpoint in volts or watts. Some of the others may, as well.