2. Generally the difference is the size (capacity) of the can, the features of the can [ease of emptying, dipstick, clear window to see level of goo etc] & whether you can mount the can in a location that is specific for (our) RHD vehicles with a charcoal canister.
3. All "Stage 2" systems that don't vent to atmosphere "VTA" are a closed system & don't stink things up. Anything with a single hose to the catch can & a filter on top will be a VTA system.
They all do the same job. A cheap can will work just as good as a really expensive one as long as it's easy to empty & you check it regularly to make sure it isn't full. If you're not into regular maintenance, get the expensive large one with a dipstick.