I would disagree that 43 mph is fast for a family coaster. It also depends on what you consider a family coaster. Expedition Everest is a family coaster and hits 50 mph. California Screamin hits 55mph at launch, and Rock N Roller Coaster maxes out at 60 mph. Besides, speed is relative... Space Mountain feels super fast due to the tight turns, but California Screamin isn't crazy as it's smoother.
Faster coaster should mean more output barring any delays.
Obviously, I would consider them to not be a family coaster. 43 mph is fast for a family coaster, which I would also say 50 mph and 60 mph would be even faster. Since you added Rock N Roller Coaster in the mix, I would hesitate to call it a family coaster. By definition, most everything would be family coaster with Rock N Roller Coaster as the upper limit. Clearly, rides at 60 mph are generally not family coasters.
Despite Space Mountain's slow speed, most people will agree this isn't a family coaster; however, people will agree Big Thunder Mountain is one at 30 mph. Perception is something one can dispute.
I have been on Manta several times in Orlando and it is a smooth coaster. Yes there are some G-forces and yes that is what a coaster is supposed to do…. Give you a thrill and a rush of excitement… It’s not a Carousel - it’s a coaster…And it does have height requirements..
Any new ride is a good ride…!