I think BC works with Automotive and Outdoor models except for
Can I use BaseCamp with my legacy Garmin device?
To my knowledge it does not work with Aviation or (dedicated) Marine models.
Can I expect more functionality the newer the device?No.
No.
It's necessary to do careful research. Following this forum is a good start, but it only deals with BC. The devices are a whole 'nother thing, and I find it near-impossible to determine which ones have what "issues." I bought a current (at the time) Nuvi 14 months ago and learned through the forums that I was much better off with an older (much older, as it turned out) device. I currently use both of them, but the older one (1490) is superior for longer journeys and both of them do strange things from time to time that I have no hope of ever figuring out.
My older devices working with MapSource ran circles around my current devices working with BaseCamp, but I need the new maps, particularly for Europe, so had to take the plunge into the dumbed-down less-functional world that Garmin currently lives in.
As I said earlier, do lots of online research. Good luck. I have made the new stuff work, but it hasn't been pretty.
BC will not work with a GPS V. It is a serial (only) model from 1999.
What you're asking for doesn't exist. This is no list or documentation that shows every feature of BaseCamp and devices showing whether they're supported or not. BC and device firmware gets updated so maintaining such a list would be difficult.
As already stated BC works with the device classes I've already posted.
https://forums.garmin.com/showthread.php?50301-compatibillity-of-basecamp-to-Garmin-devices&p=206878#post206878
That's the best answer I, and probably others, can give.
Perhaps you're asking the wrong question. What features do you want in a GPS?
I like the abillity to make a routes on my computer the way I want to go and then dump it to my GPS device. Do ALL new Garmin devices still let you do this?