For the same output setting on the floater (adjustment of vane open/close sizes), more tabs will output more chlorine or bromine. Also, more tabs last somewhat longer (not proportionately, though). So you can adjust between the number of tabs and the output setting to get the amount of disinfectant you want and how long the tabs last.
Remember that for Trichlor tabs/pucks in a floater in the pool, that for every 10 ppm Free Chlorine (FC) that they add, they also increase Cyanuric Acid (CYA) by 6 ppm. For the bromine tabs in a spa, you usually set the floater to provide a background level of bromine in between soaks while you add an oxidizer, such as chlorine, after each soak to handle the bather waste from that soak.