As far as your first paragraph, there’s an FAQ on these specific models. You don’t need a minimote, you will just use the tweaker DTH. See method 4 in the FAQ (this is a clickable link)
If I understand your question correctly, you can associate one accessory switch with each of two different master switches. What happens then is if you press master A, only the light that it controls comes on. If you press master B, only the light that it controls comes on. If you press the accessory switch, both master A and master B come on. That particular model of accessory switch can control up to five other devices.
https://products.z-wavealliance.org/products/1888/assoc?noFilename=True
If you are going to do that kind of set up, it will be best if you can just make yourself ignore the accessory switch in the app as far as its status, because its status is not going to reflect the state of your lights. That is, depending on what people do with the physical switches, there might be times when accessory switch showed is off but one or both of the lights were on. So it’s doable, but is the kind of thing that will bother some people but not others.