Girl on girl porn was one of my favorites and the one thing that would get me instantly hard (as I think you'll find is the case with a lot of straight men). Although I still enjoy it, but perhaps less so nowadays only due to the fact that once I got to experience it in person with my wife and other ladies, staged actors doing it and perhaps just for the money aspect, becomes rather blase.
Now I mostly enjoy just the standard man and woman, with maybe a third of either gender thrown in. Despite also having experience with group sex, I do enjoy orgy situations as well as the more participants in action, the better. While I view very little porn these days, due to time and desire; but when I do it is almost always in the realm of watching with the wife and we both enjoy the scenes more of true amateur couples or homemade porn, particular videos marketed as couples educational such as the Better Sex series.
As far as live cams, the only ones I both watched and participated in with my wife was with other couples. But this was back in the day when such technology was still emerging and really have no interest in such things nowadays for several reasons.
Since I can admit to mild curiosity and thus appreciate the aesthetics of certain wang in scenes of an opposite gender couple, I am still primarily aroused by looking at the woman and have no desire to view porn where the males interact with each other.
I also would have to correct you in your assumption that there is such a thing as gay porn that involves straight guys as those guys in question may claim such identity but whether they are doing it for pay or merely because they enjoy it, they are either gay or bi as well; but not straight.