I felt like I did pretty good (for me) at DK 200 last year, followed up by the Michigan coast2coast, 3 weeks later.
I followed the plan for the most part. I added in a few 60 something mile, races here and there.
But, basically I just started by doing a few 2 hour z2 rides, and then every week I was adding 30 minutes. I got up to doing a few very long rides. I think my longest training ride was 135 miles.
In my opinion you want to get a few 100 mile races in before the big 200+ race. A race is going to give you great training, better than long rides in my opinion. You get the proper motivation and are able to really mentally commit to doing the proper fueling and using your good equipment.
Otherwise stick to the plan. Don’t try and get a ton of volume in during the week, just do the TR workouts. The sweet spot and VO2 workouts will get that FTP up and improve your muscular endurance.
Finally, this is just an opinion. But if you can ride a 100 miles strong on gravel, you can ride more more more. It becomes a mental game after a certain distance. I am not in the camp that you need to really get very close to your race target distance. Good luck and have fun… you know, type 2 fun.