On a typical 35ft yacht the cockpit is small and probably only room for 2 going hell-for-leather. However, the advantage of a small cockpit on a heel is that you can wedge yourself in somewhere. When I've been two-handed, we assigned one guy to each side's rods, the autopilot (even throughout the fight) being the "3rd hand". My engine controls happen to be right at the stern, which helps. I also have a 360degree rudder, which is an immense help when reversing. This is not usual on most boats.
I see no reason not to tow 5 lures, subject to enough crew to handle it as with any boat.
My yacht can do 3~5kn directly downwind with NO SAILS in a stiff breeze. And since a launch has at least as much windage (and not much underwater), I dont see why they cant do that too with just enough power for steerage. Off-topic perhaps, but with fuel prices I dont see why they wouldn't troll at slower speeds, given suitable lures of course.
On (1), yachts have no trouble catching tuna etc on voyages with the mentioned bungy cord/400lb mono handline. This is useful because the other crew members, undoubtedly yachties, think they are in an F1 race and just the thought of slowing down for a moment is anathema to them
"I wanna put my line out"
"But Chris, we already have enough fish and the fridge is full already"
"Doesn't matter. I wanna put my line out"
..."SLOW DOWN!"
"But Chris, we're on a set course and that's a nuisance..."
More controversially (perhaps), I believe that even the wake of a yacht causes more "noise" than all the "thunderboxes" one could reasonably tow?
Even more controversially(perhaps) is that "difficulty" is worth pursuing! What do you do when 37kg line becomes "boring"? You go to lighter line, to make things more Difficult, that's what!
I regard sportfishing as continuously trying to do something more difficult or with greater odds than the individual has acheived before. Could be larger fish, more fish, lighter gear, unsuitable boats, it's all interesting and certainly a personal challenge (even if someone else has done it before).