Generally, 3 speed hubs will be geared-
3:4
1:1
4:3
I'm not knowledgeable about IG's, but I think they use 1/8"chain vs 3/32"chain for DER bikes.
Another caveat is strength.
Too low of a gear and the hub may not be strong enough if you are one to stand on the pedals. Especially if you have some old Shimano 333's.