The answer is: too many variables to give a good answer. type/consistancy of live rock? Has the tank been fully cycled? How much rock, how much sand, what kind of sand, etc. Too many variables. Aquarium keeping, whether SW of FW is all a controled experiment and comes down to chemistry. Amonia is not your friend, but like the stuff you flush, or the stuff you pickup with the scooper in the back yard, its a byproduct of most living things. You cant avoid it. A tank without amonia is a tank filled with AIR and nothing else. So we come up with ways to deal with the amonia. The live rock/sand will be colonized by bacteria that eat amonia, they give off their own "Stuff" which is nitrites. THis "Stuff" is eaten by other bacteria and they give off Nitrate. Each level of break down is less toxic to marine life, but still has to be dealt with. Closed systems are a paradox. They keep Enclosed that which wasnt designed to be enclosed.
What do we do? age old question, with better answers every year. We place lots of rock and sand, so the bacteria have places to attach and live, We do water changes to keep the "bad Stuff" from building up. We filter the water through GFO/Carbon and other materials to try and remove this "Stuff" We house micro algae, either in the DT or in a seperate "Refugium", or run Algae Scrubbers...in an attempt to allow and encourage growth of things that Eat the "Bad Stuff".
There is no easy answer to your question. The more heavily stocked a tank is, the more that will ahve to be done to remove the "Bad Stuff". Water changes are one method(10-20% as needed) and are SOP Even if all you have is one fish in a 200g tank.
In comes the "Keeping" part of the equasion. We test and monitor our tank, we do research on the critters we want before we buy them, and adjust the Export measures as needed. Understanding biological breakdown is critical to keeping a tank stable, and all your critters healthy.
SO to sum it up. More live rock, good, more sand, not so much. Cycle the tank with all the live rock you intend to add, and get really good at testing the water parameters. Of all the things you might find in your water, Amonia is your top enemy, with Copper being a very close 2nd. Avoid using untested tap water, and run a RO/DI to remove any copper and other bad stuff. Test often. The bigger the system the more stable it will be, but even a 10k gallon system requires testing.
Add livestock Slowly. Add a new fish(Post QT), wait a day or 2 and test for amonia, if you see a spike, its NOT safe to add another. Once the amonia spike goes away, wait a couple more days and adding another should be safe. At some point, depending on how you want to stock, you will get to a point where the amonia spike takes longer than a week to fade. Thats the cut off IMHO. if you want to add more, you have to increase measures to remove "Bad STuff". More rocks, adding a refugium, Media reactors(carbon/gfo are common). Protein skimmers, uv sterilizers, etc.
Bottom line, you have to find out the limits yourself, just go slow. When your system is struggling to process the amonia, you are borderline overstocked.