A floating baffleboard is affixed to the cab on only two sides. A board could be affixed with screws but not be a floating board if it was affixed on 3 or four sides.
The thickness of the board might render the question of the difference between floating or non-floating moot. In Tweed Fenders, the floating baffleboards were thinner than BF floating boards and therefore able to react to the vibrations of the speakers. Tweed amps are more organic due in part to the reactive nature of their cabs. Larger speakers demand more support and therefore thicker boards. Thickness brings stiffness and loss of the reactive nature. Gluing the board into dadoes stiffens the board even more.
Depending on what the player wants, non-floating boards might be preferable....tighter, cleaner sounds with quick attack. Floating boards won't yield that tight sound to the extent that a non-floater would.
Regardless of thickness of the board or how many sides are used in the attachments, I prefer one-piece baffle/grill boards. I don't care for velcro-attached grill boards.