Audio editing can help intelligibility, but this requires skill, practice and tools. Simply capturing and playing back audio without modification to the signal, gives surprisingly poor results in many cases.
Building a rapport with the people on stage will go a long way to solving problems, when someone is too loud or wants more than you can give them in the monitors.
Those who are on the platform need to have an immediate and true sense of the congregation’s “voice” which is, after all, the most important musical element in our overall sound.
Your congregation's perception of what is "too loud" during your services can be heavily influenced by quality of mix, sound system, acoustics and musical dynamics.
Being an audio engineer during a live service means that you have hundreds of small decisions to make, which directly affect the quality of the overall mix.