Not very useful. I wanted the P74 so I did the SL8 and S-Works Venge, then hastened the process with the Allez Sprint. Also doing the Aethos sometimes now that I got there but mostly upgrading the P74 in group rides. SL8 for races.
My choices of Zwift frames are
Zwift Carbon, which I have fully upgraded
Zwift TT, since all you have to do is ride. Put time in.
Zwift Mountain Bike, easy to get the elevation. I have done workouts on the Aple, pretty simple.
On the new Fuhgeddaboudit route, I primarily rode the Zwift TT, and switched to the Zwift Mountain bike on the bigger climbs like the NYC KOM and the longer climbs up to the glass roads.
Fairly pointless unless Zwift decides to put a randomly changing surface on Tempus Fugit with sand drifts - these sand drifts over the road would favour gravel bikes and MTBs and slow down all road and TT bikes to a crawl. This would really make the robopacer groups and races on Tempus more dynamic.
My upgrade process was SL8 S-Works, Aethos and S-Works MTB, the latter two doing daily 1 or 2x ADZ laps. That got me the Project 74 quite quickly. No workout modes on ADZ used, just shifted gears and went with the gradients.
Then the Cannondale I went CAAD, the Cannondale Evo and one of the other slow Cannondale bikes to unlock the R4000. That was a miserable slow process, all those bikes were so slow and you have to do heaps of distance on them…
I am currently about 1400km away from level 4 on the Project 74.