Are trainer road plans worth it for outdoor training?

Yeah depending on where you live then finding long stretches of road might be hard. Maybe consider driving somewhere to complete the FTP test and then you can do most of the other workouts where you live. Even longer intervals can be done if there are a few interruptions. If you have to pause a couple times during a long SS interval because of a stop sign it’s not a big deal. Long stop lights would be different though.