I've been asked a lot of questions about the new World builder items, so I spent some time to study them.
The snow has a couple of limitations you need to know about. Firstly is the size, the way its designed, is as you enlarge it, the spread of snow becomes thinner and the smaller it is, the more compact the spread. Think of it this way, within the snow box, theres say 100 snow flakes drop per second, now if you enlarge the box to cover a world the size of Havasu, there's still 100 flakes per second dropping, but evenly spread over that entire world, so you will be lucky to see a single flake every now and then, but you will see them.
The second is the fall distance, this is limited so it can cause problems if you are using it on very uneven ground or different levels within a single area. An example is a 5-story building of mine, I had the snow set so I could see it on the top floor outside the window, but there was no snow visible on the ground level or first floor.
The other item is the teleport pads, the only issue I came across with these is they need to be very clearly above the floor surface, if even slightly hidden below, they seem to foul and not work or not work smoothly every time. There an icon with 2 feet pictured, make sure that is clearly visible. Its not like the spawn point, where you want to keep that as close to the floor as possible so you're not elevated in the air upon spawning.. The teleport can be many inches in the air with no side effects.
I don't believe any of these are bugs, but rather limitations on the design of what we have, maybe they can change/fix them but going off other things implemented over the years here, I wouldn't count on this ever getting any attention. So with this in mind, make sure you understand these limitations and you will go a long way to be able to work around them. For starters, the entire room does not need covering, its like the fog, you only need to cover what you actually walk through and see from your point of view and at the points of interest in your worlds.