Largest capacity hard drive for Gen 3 Drobos?

I’ve got two Gen 3 Drobos maxed with 4 x 6TB drives each. Will they support 10TB drives?

And will a 5C power supply work on a Gen 2 or 3 drobo?

For a Gen 3, the largest capacity Drobo have tested and qualified, according to this page is 12TB.

I strongly recommend dual redundancy using huge drives in a gen 3 (or 5C), see my answer to the question you posted for drive sizes in a Gen 2.