The featherfin would be fine in a group of 3 and they would have plenty of space in a 60 gallon! But get whatever ones you want. Since your tank is bigger you could get around 15 Cories. They sell the featherfin at Petsmart if you have one close.
But before you decide which fish to get go on YouTube and watch videos of each. IMO I think the Featherfin have more personality than Cories. And I just watched videos and 2 Featherfin would be fine together. The only downside to getting the Featherfin is just one costs $17.19 but getting Cories would cost $6.50 per fish.