Assuming a map has no fog on it, does VBL only prevent showing tokens on the Token layer? I'm noticing that thing on the Object and Background layer will show for a player, even if the VBL blocks their vision of it.
Am I doing something wrong? Or is this just the way that VBL works, blocks sight of non-owned tokens on the Token layer ONLY?
You might have a misunderstanding of the purpose of VBL. VBL and FOW work together. Without FOW, a players token sees everything on the map excluding stuff on the token layer. This makes a certain level of sense when you follow ALL of the possible paths of logic.
The point of VBL is to either:
a: prevent players from seeing enemy tokens(no FOW)
b: prevent players from seeing both enemy tokens as well as unexplored areas(with FOW).
In the latter, under normal circumstances, a player won't know whats in a specific location until he sees it with his own eyes. After which, it almost certainly does not change (room layout, room contents, etc) OTHER THAN creatures when he leaves the room and has no direct line of sight on it.
Bottom line, if the players are in the first room of a dungeon and you don't want them to see the entire layout, use FOW, that's what it's purpose is!