As I understand it, Corona has basically just opened the door for you to use Particle Designer ($50), which seems to be the current Photoshop among particle visualizers (at least, for game/app developers). If you want to spend your time making the perfect particle setup without code, PD seems to be a great way to do it, and it may save you some time because the full UI suite gives you a way to quickly iterate and try out different effects.
I can’t speak to Particle Candy apart from saying X-PRESSIVE have supported Corona SDK for quite some time, so their code is probably quite solid, but I’m not sure they provide a visualizer. I can speak to CBEffects (free!) which works great but basically means you have to write code to try it out, as there’s no outside visualizer. But both support G2.0 now and are perfectly valid options.