Coeus
Striker
Clarke is more of an inverted winger. Natural wingers play on their natural side and generally look to go on the outside, and an inside forward is essentially a striker who starts in one of the channels/half spaces areas.
An inverted winger starts wide but generally plays on the 'wrong' side, hence their desire to cut inside. That's Clarke.
I think inverted wingers and inside forwards are very similar. Id suggest he was a forward as he was more likely to shoot where as Roberts for example is just as likely to put in a cross. As was Johnston.
Either way, my point is, to my mind, for you to be classified as an inside forward, you have to be positioned wide at some point in order to be considered one. Someone who is routinely central can not be.