Book recommendation; Cyclists Training Bible. I'm 65, ride 10-15 hours/week and train with a coach.

To your question about Just Ride days, I define that as riding how my legs feel, some easy, some hard, cafe stops, and I do that when I ride with friends about once a month. Everything else is training focused, and especially the long duration/easier rides which require discipline to stay chill and not hammer.

We actually obtain the increases in speed and strength during rest weeks, so taking that easy week - days off and only super easy rides - is key.