I fully intend to make sure there is a fully supported filament path, regardless of any other choice I make for the extruder i.e bowden/direct drive, geared or not, single or double sided drive.

Just a question, what sort of speeds do you print flexiblez at on your bowden? And what sort of speeds do you print at in general?

The double sided drive and geared extruders from what I understand only really shine with high print speeds, you dont need the extra grip and torque at 80mm/s but you might at 150/200 mm/s