I’m not quite sure what you want to be honest, mate.
But I’ll give you multiple advices in hope you’ll get what you need.
You can always increase the overall resolution of your mesh then apply it so that when you add additional edge loops your mesh won’t lose that much roundness. You can also use crease edge option(Shift+E) to sharpen your edges without the need to add any additional edge loops, note that your subdivision modifier would need greater subdivision value of 1 in most cases.
Now, there’s another method that will help you in conjunction with techniques I’ve mentioned previously. That method would require you to model a base mesh of your and have a subdivision modifier with high value. You could use this base mesh for retopology, you can add mesh onto your base mesh with shrink-wrap modifier or with snapping onto surface option, the choice is yours.