- If you plan to follow TrainerRoad plans and workouts, using Virtual Power with your trainer, you MUST follow the settings they define. So, use the trainer setting at exactly what they assign. That is the only way you will get the proper Virtual Power data that corresponds to your training zones.
- Using any other setting, without adding a dedicated power meter, will give you different VP data, and will likely skew your training.
This site shows two settings (4/10 and 8/10) of the trainer for comparison. It’s far from comprehensive or enough to draw any real conclusions
You’d really need a power meter and to perform the comparisons you mention to learn anything useful outside of using RPE. I’d ignore those options and follow the TR setup.