To find your sweet spot with a given juice it's best to try various resistances at various voltages/wattages, as different juices taste better at different temperatures. It's not much different to cooking different things at different temperatures to get the best taste. The are a variety of devices that cater for different resistances, like carto's, Vivi Nova's, well most things with replaceable heads. Whilst RBA's can be built to almost any resistance, they lend themselves more to use with unregulated devices, because that way you can build your coils to suit the power delivery, rather than adjusting the power to suit your resistance. That's not to say you can't use RBA's with VV/VW, there are numerous people who do, but it's less necessary than with something like a 3ohm carto that would be very underpowered on a mechanical mod.