At the end of "Endgame," the Borg transwarp hub was destroyed. Does that have any effect on the transwarp conduits that are generated using the transwarp coils on Borg vessels?
They would be unaffected
In explaining the technical side of a transwarp conduit, Memory Alpha explains that:
The Borg maintained a network of thousands of transwarp conduits throughout the galaxy, connected by six transwarp hubs supported by interspatial manifolds, with exit points in all four quadrants. They were additionally able to generate new conduits through use of transwarp coils.
So, as long as a Borg ship was outfitted with a transwarp coil, it should be able to generate its own transwarp conduit, irrespective of whether the transwarp hub was working or not.
Actually yes. As Borg uses hive minds,they have a share-tech as well. So as the hub gets destroyed,their vessels (both Cubes and Orbs) lose their Transwarp drive. Their Transwarp drives are dependable not on Subspace used by both Warp and Transwarp,but on condition of the hub which controls all the drives. Let me put it this way: With Warp drive,if the subspace collapses,the drive drops out of speed and the ship either comes to a full halt or switches to impulse drive (the kinetic power plays no role here since there's no gravity to support the drive necessary to achieve kinetic forward movement) while Transwarp hub causes a tunnel effect which (the hub) uses stabilisers to facilitate additional sturdiness to the Transwarp tunnel thus negating the Subspace collapse. Hope this helped.
Consider it this way. The Borg hive mind mentality is kinda like shareware website filled with information about almost everything. And their technology is pretty much the same. It is shared between the Borg mothership and Cubes and Orbs. That's one way,besides the hive mind,to control drones. And the Borg "queen bee" has the ability to disconnect a separate ship (the renegade drone Cube in Voyager series lost their Transwarp upon the mothership learning of their rebellion by a push of a button at the hub) as well as powering down the entire Transwarp system. Transwarp depends on the hub straight and simple as seen both in Voyager and Enterprise series.