I also have the 29g biocube and enjoy it immensely.
I spend maybe an hour a week on it total. That includes the water changes of 3g a week and changing out the filter floss every few days. I usually scrape any algae from the corners every week or two takes another 10-15 minutes.
Now when I first started the tank I spent more time with it. between testing and water changes and other things I spent more time on it. But it has stabilized so it's almost care free now. I am also just running a fowlr
for now as I have 2 other reef tanks already.
I'd reconsider corals, I think the easy ones are just that, easy. Once your water parameters are good you can add some zooas or mushrooms in with no problem.