That live rock should be awesome! When I started my 15g back in 2011, I got cycled live rock from the LFS, and it was really fun as it came with all sorts of small creatures. Also, there was really no cycle to speak of.
The tang discussion; I'll be in the minority but I say it is possible, but go really slow. My own progression was a Yellow, then added a 3" pacific blue (aka hippo) that a friend gave me as his tank was crashing. The fish were small, and this was a 20g tank at the time. Shortly thereafter, I moved it all into a 40 breeder (mixed lps/sps/zoa/nems). The local LFS had a very thin, ich'ed out sailfin that I took home and put in my small cycled spare tank with rocks full of bryopsis. It ate all the bryopsis, kicked the ich, and went into the 40 with the other fish. 10 years later, the three are still together in my 93g. This was all done over time, and my tanks have always had algae for the fish to graze on, which I think is a key point to keeping them happy, at least for the zebrasoma and any grazing fish. The blue doesn't graze, but is still the fattest of them all, lol. I've had ups and downs with the water quality, high nitrates and phosphates (I like fish but couldn't do water changes enough). This is currently solved with a sulfur denitrator and GFO, after first knocking the phosphates down with Lanthanum. Water quality is now the best it has ever been in this current tank. I realize this isn't recommended tang-practice, but wanted to add my personal experience. Interestingly, though I've lost other fish, I haven't yet had a tang die on my (touch water..). 2 weeks ago, with some trepidation, I added a 4th fish, which is so far doing very well.
To reiterate, don't be in a hurry to have a lot of fish; spread it out over months and years. Also, for a lot of these fish, sterile new tanks are no good. Pop a new fish into an aquarium with live rock with biofilm, detreitus, algae and it may just settle in within a few days.
The tang discussion; I'll be in the minority but I say it is possible, but go really slow. My own progression was a Yellow, then added a 3" pacific blue (aka hippo) that a friend gave me as his tank was crashing. The fish were small, and this was a 20g tank at the time. Shortly thereafter, I moved it all into a 40 breeder (mixed lps/sps/zoa/nems). The local LFS had a very thin, ich'ed out sailfin that I took home and put in my small cycled spare tank with rocks full of bryopsis. It ate all the bryopsis, kicked the ich, and went into the 40 with the other fish. 10 years later, the three are still together in my 93g. This was all done over time, and my tanks have always had algae for the fish to graze on, which I think is a key point to keeping them happy, at least for the zebrasoma and any grazing fish. The blue doesn't graze, but is still the fattest of them all, lol. I've had ups and downs with the water quality, high nitrates and phosphates (I like fish but couldn't do water changes enough). This is currently solved with a sulfur denitrator and GFO, after first knocking the phosphates down with Lanthanum. Water quality is now the best it has ever been in this current tank. I realize this isn't recommended tang-practice, but wanted to add my personal experience. Interestingly, though I've lost other fish, I haven't yet had a tang die on my (touch water..). 2 weeks ago, with some trepidation, I added a 4th fish, which is so far doing very well.
To reiterate, don't be in a hurry to have a lot of fish; spread it out over months and years. Also, for a lot of these fish, sterile new tanks are no good. Pop a new fish into an aquarium with live rock with biofilm, detreitus, algae and it may just settle in within a few days.