I hereby recommend that there be a preformance mode, like recently or normally the app takes a while to load on slow systems and I think that it would be amazing for there to be a preformance mode pretty little near the lets go button and that would be pretty good for people with slower PC’s and it would make a lot more people want to try out Zwift, etc. Also it would be pretty cool to have a “Solo Ride” mode where you ride by yourself and you can’t see anyone else and you can just go around and look at the scene (On Your Bike).
For your last request: You can already do this. Just load up the game as normal, then disconnect from the internet. All of the other riders will disappear and you will be alone in the game. When you get done riding, just reconnect to the internet before saving your ride.
Alternatively create a meetup with a friend you know won’t be online, then you can just ride solo.