I can chip in a bit.
Got two makerbot clone direct drive machines and one 200x270 delta with a one sided drive. Ie: grooved wheel pushes the filament against a single hobbed bolt on a bowden system.

the bowden prints faster and with at least as much precision. It will also print ALL flexible filaments, faster than the direct drive machines.
Even ninjaflex and filaflex.

So going on recent experience - you definitely do not need a double hobbed bolt drive setup.
The really important thing is to make sure there are NO gaps anywhere in the feed system. Filament must be given no alternative route right from the extruder to the nozzle. I think that's why the bowden setup prints flexibles faster and better than the direct drive machines. I've eliminated any gap in the feed system and got the feed tube down to it's optimal (shortest length without sharp angles being able to form) length.