You mentioned you don't like maintenance, and both versions of the Legacy really do require some maintenance. There are much easier devices out there, so I guess the Legacy wouldn't be so good for you (although if you get comfortable with the maintenance it is very rewarding). I'll answer some other questions for the record, just because I'm a fan.
Yes, there is a dedicated on-demand function, and it works well. However, for whatever reason, the Legacy seems to operate perfectly in session mode, with slightly less hassle. When you're not drawing, it's not vaporizing, so the material stays fresh, and you don't have to wait for heat-up. But some may prefer on-demand. Both are easy.
There wasn't any version 2 (except the Pro). But after the original came out people started modifying it in all sorts of ways to work better, and that led to them distributing an extra part that made it all work better. It was kludgy, but it worked well. It wasn't so much that the material was near the heater, but that the hot air came up in a narrow column, and that darkened some parts a lot while leaving others greenish.
AFAIK the pro is available everywhere. It improves some things over the OG, but Airvape isn't what I'd call strong on design. They have some great ideas, but from an industrial design standpoint they're rather weak. So the Pro is better in many ways, but not really a leap forward. More of a clumsy step or two. OTOH, it hits much, much harder.
The device is really perfect for a certain kind of use. Perhaps someday you'll enjoy it. Good luck.