As above, pretty consistent if you keep the resistance, tyre pressure and roller preload the same each time. Mine ‘sort of’ tallied with my stages, at least my FTP was similar on both, but wandered a bit as the room temp went up. That could be specific to my turbo though (a Tacx magnetic).
For me it worked fine. I find it hard to hold a certain wattage, even reading the 10s or 30s avg it fluctuates too much. I find it easier to ride to rpm. So if the workout calls for, say 300w, I find a gear that lets me hold 300w at about 90rpm and just watch the rpm instead.
Do an FTP test as soon as you can so TR can ‘scale’ your intensity to suit!