Doesn’t matter what “plan” you do on TR. Any of the base / builder repeats will be perfectly fine. Seriously. You’ll likely be off the plan all Spring as you build up your endurance anyway.
In my humble opinion, you need to work on the mental training if you’re jumping into multi-day events. In the Spring, go out and do a really long and hard ass ride. Sleep less than five hours and repeat the hard ass ride. Nothing teaches you how to do that more than experience.
Find a riding club this Winter that does stuff like this. Doesn’t matter whether it’s an ultra, bikepacking, or Audax club. Build up till your ready for a multi-day really long event. Then go do it. Failure is just as educational as success. Nothing wrong with getting knocked down a peg or two and then learning from the folks that were successful. Has worked for me a time or three. 