I’d do more than just sweet spot. Also add VO2/threshold and endurance rides.
What volume plans are you planning on doing, and are you doing additional outside rides in addition to the TR workouts?
If you are doing low volume TR plans, one thing to be mindful of is that these plans include a good amount of threshold workouts. You can dial some of these back to sweet spot if that would be too much intensity for you given additional outside rides you might be doing on top of the TR plans (this is what I’m doing).
In case you are interested in the physiology side of things, for a ride like the Maratona you’ll want as high a VO2 max as possible, and low VLaMax (combining to give high FTP).
VO2/threshold and endurance rides boost VO2max.
Low cadence sweet spot/tempo rides reduce VLaMax.
The distribution of workouts across these types of rides will depend on how many hours per week you are riding, and how well you recover. A pyramidal distribution is a good place to start. You can do this by taking a TR low volume plan, adding longer outside rides, and dialing down some of the threshold workouts to SS/tempo.
This thread is a good one to read through to learn more.