Which is easier to maneuver, 25ft+20ft, or pickup+30ft FW?

I can back my TT a lot easier then I can back my 5th wheel, but my 5er is 10' longer then the TT. As others have said I would get the one you want.

A standard bed CC pickup truck pulling a 30ft (again hitch to bumper) FW?

Because of the amount of the fifth overhang over the truck bed, the actual length of both the truck and fifth will be about five feet shorter than both measured separately. Of your choices, I would think that would be a little easier to maneuver after a few dry runs getting used to the fifth's turning and backing characteristics.

The 'C' and the trailer will be around 45 feet long perhaps a little longer with the hitch, about the same as the truck (short bed/long bed?) and fifth. I would get the one you want and practice a little and you should be good. There are many on here that are adept at putting a 35-40 foot fifth where they want it so it can be done. Once a fifth starts backing up in a turn it tightens so in some circumstanaces it can back into tight corners. If you get a slider hitch (short bed) or if a long bed you can usually go to 75-80 degrees of angle depending on the fifth's front nose cap and that can be helpful in backing into tight spots as well.

With practice any setup in comparable length will get easy to maneuver.

The problem will be if the roads are too narrow or turns too tight. There is a point with any setup where it is impossible to get where you need to be no matter how practiced you are. When you run into something like this then you either find someplace else to park or use some other means to get everything parked...like take the trailer in to the spot using a forklift or powered trailer mover and then park the truck or B+

I would guess that a central pivot point (one half the total length) would be best.

Because a 5th wheel pivot point in above the rear axle and it tracks inside the wheel tracks of the truck, you cannot take as tight of a turn as a bumper pull. Think of semis that have to swing wide on tight corners to avoid jumping the curb.
With bumper pulls and the pivot point behind the tow vehicle, it lessens that problem.
Difference in trailer lengths also factors into the turn.