As not a runner, I could be pretty far off but I'll throw in my two cents:

Since cycling is generally low muscular impact, I would avoid low cadence all the time. Certainly there are times when you may end up pushing hard, its just likely not at a low cadence. Now that does not mean to avoid working on higher gears... It just turns into intervals...

So, If you want to work on improving you bike fitness, I guess it would be intervals for strength and speed, and FTP, with good recovery in between. Don't just throw your bike in a high gear and think that will do it. That will lead to bad habits and bad knees.

Since you have a trainer with power, I'd work to that, likely at a cadence between 80 and 100, varied up a bit to broaden your comfort zone. Maybe it has some nice training routines built in.

If you're in college or something maybe you could find a coach or something related to your other activities?