Advantage play is the combination of a good bonus and good knowledge of the game so you can pick the correct game and strategy to make the most of a specific type of bonus. There is quite a bit of math and knowhow involved here.
Bonus hunters just seek out the best bonuses to play.
None of the above players are breaking any rules and they are perfectly within their rights, it’s up to the casinos to design foolproof welcome bonuses or to rely on loyalty bonuses only.
A combination of these two is what many casinos call bonus abusers.
Then there are cartels, or rings, or groups who defraud the casino by using various IDs and IPs etc to sign up over and over again to take the same generous bonus. These are doubtlessly criminal.
But all the terms are so jumbled and used interchangeably that it’s almost impossible to have a conversation about this.