1) I've found lots of High Metal and Metal rich bodies. Some are landable some not. Almost all of the ones that aren't landable, are planets or are moons with an atmosphere and pay something for being found (EDDI will tell you the exact amount). None of the ones that are landable though pay squat (at least the EDDI robo voice doesn't say they do). ?????
Landables pay plenty. I don't know why EDDI is telling you they don't, but it's lying to you. The most valuable planets in the game (Earth-likes, Ammonia worlds, most terraformables) are not landable.
2) Mapping the landable moons should be a big deal and pay a bunch especially considering that they have lots of good stuff to scrape off of 'em.
Well, consider that "landable planets" are as yet only partially implemented. Other planets ought to be "landable" too, we're all just choosing not to do so at the moment. Apparently. If/when we do eventually get to land on those other planets, they will no doubt also be full of things to harvest, shoot at and scan.
3) I've found one water world so far. I expect UC will pay for that but EDDI doesn't mention any pay off.
Waterworlds are valuable. Terraformable water worlds are ten times more valuable.
I've mapped a lot of moons, rings and planets. It takes a lot of time or used to anyway (once I figured it out 2 or 3 probes will get you to 100% and it takes mere seconds to launch them - large planets take a few more and you might have to move the ship some but still - easy). Exploration is borderline interesting but not what I would describe as fun. What will I end up actually getting paid for. Currently I only spend time surveying systems with 5 or more bodies that aren't companion stars of the jump in star. Is there a way to rapidly identify a system as worth mapping? If so how would one go about doing it?
Currently in a part of space that is 95% Red and White dwarf type stars witht the closest human system being almost 500 LY away (just started on my trip out). Is that a problem.
Some star classes are better at hosting valuable planets than others. red dwarfs (class M) and brown dwarfs (classes L, T and Y) are cold, dim and boring - all they usually have around them are iceballs and the occasional CLas I gas giant, neither of which are ever worth much. Class K and G aren't really that much better, though do have higher probabilities of finding valuable things. At the other end, Class B are hot, usually way too hot for any planets around them to be habitable and therefore just as likely to host only non-valuable worlds; lava worlds may look cool but don't pay much. If it's max credits you're after (and max chances of finding Earth-likes), swich your galaxy map to filter view, then filter by Star Class, then deselect everything except A and F stars. Those are where the money's at.
Is everyone mapping all the planets they discover? I only bother with the interesting ones for landing on (photo ops) and the earthlikes. Should I be mapping more? I'm at Triple Elite, so I don't have progress to chase.
As for mapping, it's entirely optional. If you want to roleplay being a Starfleet science officer, then by all means map everything if you wish. As far as the game itself is concerned, Mapping gets you locations of surface features, and two long-term rewards: credits, and the "Mapped By" Tag. If you don't care about either credits (and the Exploration rating progress towards Elite that comes with credits) or the Tags, then you don't have to map anything at all, unless you're looking for surface features. Personally, I'm Elite Explorer and have over a billion credits in the bank, so I never map anything except Earth-likes, unless I'm in an interesting system that's only been partially explored and I want to plant a "Sapyx was here" flag. But for maximum "credits per hour", you don't want to be wasting your time mapping a bunch of iceballs or rocky moons and certainly don't want to be wasting time mapping gas giants. Map the Earth-likes, Ammonia worlds and Terraformables, and leave everything else.
Note: the FSS will not tell you if a world is terraformable or not (it will tell you once per planet class per region, through the Codex popups, but that's all). To find terraformables, you first have to do the full FSS on the system, then open the system map and click on each HMC (high metal content planet), Water World and large Rocky moon (above 0.40 surface gravity) that's within the "goldilocks zone" for that particular star. After a while, you get pretty good at locating the Goldilocks zones (the third-party tools can also do this) and at guessing which objects will be terraformable and which won't.