The steeper angled frogs would be harder to push and I don't see the need for them on a jointer. My 45 degree frog seems to work just fine. Get it sharp, set the chip breaker close to the edge of the iron in more difficult woods.
I go for the longer plane (#8) on edge joints of any length over 36 inches. It is a matter of choice. the bigger plane handles nicely for me. I have the other options as well but If i had to pick only one it would be the #8
Would there be a time that, if one had a #7 they needed or wished for a #8? In my case I have a 4 1/2 so the blade is the same as the #7 not that one goes around changing blades all the time, but would be convenient not to stop and sharpen...just change and keep planing.
With a bevel up plane you loose the advantage of the chip breaker, if you work a lot of end grain, like cutting boards, the bevel up could be an advantage. The chip breaker makes the high angle blades unnecessary.