Is it really necessary to stick to the more intense and popular routes on Zwift for power workouts, or can riders achieve the same level of effectiveness and challenge with less crowded and less uphill-focused routes? For example, would a rider see comparable gains in power output by doing repeated intervals on a flat route like the Tempus Fugit or the PRL Full rather than tackling a steeper incline like the Alpe du Zwift or the mountains of Watopia? Are there any specific routes or features that riders should prioritize or avoid when designing a power-focused workout on Zwift?