small external drive
a few terabytes
I shudder to think what you consider big.
Anyway, you won't have any issues with it, but if you're going to use it for any length of time and not go back to Windows, I'd change it to something like xfs or btrfs. Hopefully it's less than half full so that you can just shrink the partition, create a new one, move the data, delete the old, expand the new. If it's more than half you might need to do it in steps. If it's basically full, don't bother because it's more trouble than it's worth.