IME iron bacteria still makes it thru an RO, although it doesn't cause as many problems. Try running recommended GH 3-2-1 with untreated high iron stinky water and it will grow things quick! just not plants/roots.
I run my RO into holding tanks and treat it with a homemade ozone setup that gets the ORP over 400 on a timer. It goes down quick in between. Before using pool shock I was still having issues. I consider it a miracle thing, really. BUT there were other elements in play that may well have contributed to overall poor root health like not running straight mineral nutes, & using the wrong profiles.
I've got someone using pool shock in 5 gallon buckets, no light proofing, water temps hitting 80, tiny aquarium air pumps and growing some big rootbound monsters. High iron (but doesn't stink, so limited bacteria) well water. The stuff helps you cheat and doesn't seem to hurt (unless paying UC roots prices!)
To me the biggest benefit of the RO is it gives you a clean slate to start with. You might have a decent balance in your water, you might not. You might be able to read the plants and make it work great, or your water may cause you to struggle. Getting an analysis isn't that much money and would go a long ways in determining whether or not you need an RO, and how best to work with you water. It would seem to me that in a super low EC game, RO is the best bet. But I understand the efficiency aspect.
Eventually I want to make my RO from a holding tank of pre-treated water along with a dedicated pump etc. But i'll need more space for that. Currently using basic '7 stage' RO/DIs that produce ~60gpd. Just added a second one as a bandaid to up production.