They're not really a spotted version of the common bumblebee, though they do belong to the same genus. If I was to hazard a guess, I'd be looking at things like Brachygobius mekongensis or Brachygobius xanthomelas. But all these gobies are incredibly difficult to identify to species level.
Whether or not all species need brackish water is a much debated point. It certainly won't harm them being kept in brackish water, but the biggest issue tends to be food.
Bumblebee gobies fall into two size brackets, the "dwarf" species at about 1.5 cm in length, and the "regular" species at around 3 cm in length. Beyond that, they're all much of a muchness.
Cheers, Neale