For fixed route transit, speed is latency. The faster the bus can make the average trip, the tighter the timetable can be given the same number of buses. Fewer stops also improves consistency which means you can plan to arrive at the stop closer to the scheduled time, and timetables can be tightened even more by reducing the layover times that keep the bus synchronized with the time table.

Separately, the variability problem can be somewhat solved with the real-time location updates that many agencies provide. You'll still have to wait the same amount of time, but some of it can be done comfortably in your house when the bus is running late.