Adding capacitance to a "linear" driver design is one way to reduce modulation, with some tradeoffs. There are other power supply designs, such as switch-mode and several variations of "constant current" drivers, which could reduce modulation at a higher cost. Adjusting the frequency also plays a role in mitigating perceived flicker.

In higher-end drivers, you'll often see a hybrid approach, such as constant current between 5 and 100% and PWM below 5%. Drivers with deep dimming down to 0.1% are just using 10-bit PWM. This would be difficult to do in a bulb form factor.

I haven't seen any meaningful research into the persistence of various phosphors. It's an interesting thought. My guess is that there could be some effect, but usually we would just try to improve the power electronics.