Which kind of regulator/battery setup should I use for 5 volt microcontroller and transmitter circuitry for optimum performance?
I would estimate that your most efficient solution is to use a low power regulator for your microcontoller and let the microcontroller activate a buck regulator to feed power to the radio transmitter. This will mean that in idle mode only the low power regulator's current consumption is discharging the battery.

Of course this means an extra IO line to "enable" the higher power regulator AND some shortish period of "waiting" whilst the radio becomes "ready" for the data transmission from the microcontroller.

The problem with NOT enabling/disabling the higher power regulator (feeding the radio) is that its quiescent current consumption might be hundreds of micro amps or even low milli amps and this will certainly deplete the battery.