The 48" mulch kit will work best with the Exmark mulching blades.
It can mow warm season turf at low heights with a bagged appearance, in one pass with normal growth, or two to clean up small windrowing if it's tall stuff.
The higher you cut the less crisp the cut as it doesn't get as much vacuum power to stand the grass up. Above 3" it's going to leave stringers in some situations.
Floppier, less rigid grasses won't cut as cleanly as when discharging.
Overall, if it's your only mower you are going to run into situations where a mulching kit would not be the best choice from time to time. You'll have to decide for yourself if you save enough vs bagging on routine yds to justify the extra time to double/triple cut the tall ones. You'd also have to decide if the cut was what you wanted. Mulching saves me tons of time vs bagging but I mow mostly Bermuda or Zoysia at 1.25" to 2.25" and it mulches quite well.