The only variation I hope to see is just based on what the human was before it became Infected. Thinner, smaller infected humans would probably be a lot weaker and faster, while fatter infected could possibly be a little stronger (especially in physical attacks) and also slower. If a soldier perhaps got infected, they could still be wearing their bullet proof vests and such so they have extra protection.
In basic, they don't necessarily have any variations such as shooting acid and wacky abilities like that, but rather just their strength and speed is based on what the human itself was like before infection. Would seem the most realistic and reasonable route to take for varying the Infected.