Hello there, welcome to this addictive hobby. Please allow this humble newbie to try to answer your question because I can't stand the silence. Maybe the sifus here will chip in later.
Option A, I guess would be a cube tank with your existing HOF. Pros: its the cheapest option. Cons: you won't have anywhere to hide your equipment should you decide to add in things like a skimmer, auto top-off, reactors...
Option B, the IOS tank. Pros: you can hide all the stuff. Cons: bit more expensive than a simple cube tank unless you're getting those nice ADA ones.
Looks like your veering towards a nano fowlr (fish only with live rock) set-up? Maybe you can add some hardy soft corals later, like mushrooms and leathers. You can go check out some nice nano set-ups at LFS like aquamarin, ah beng. Then decide on your tank, get some live rock/sand. Get a hydrometer, mix your salt and distilled water and you're good to go. You may not need a skimmer if your load is low and you change water regularly. You can use fans to keep the temp down.
But remember to let the tank cycle properly before your add anything. I made the mistake of stocking too fast.
Cheers and good luck with your tank