Good questions @mccabe.pierre, here is some more info:
FULL CENTURY:
GOAL
To get you ready for a ride/event of 100+ miles and less than 1,500 meters of climbing
BEST FOR
Riders with at least five hours of riding a week for the previous 2 months, have 5-9 hrs/wk available to train, and can ride outside over the weekend
TRAINING BLOCKS
2 weeks on, 1 week off
PLAN ENDS WITH
Event day: full century
SPECIAL NOTES
This plan contains a mix of indoor and outdoor rides, with the longest sessions being outdoors and occurring over the weekend as long as you select a Sunday as the end date.
Mountainous / Hilly Gran Fondo:
GOAL
To get you ready for a ride/event of 80+ miles and 1,500+ meters of climbing
BEST FOR
Riders with at least six hours of riding a week for the previous 2 months, have 6-11 hrs/wk available to train, and can ride outside over the weekend
TRAINING BLOCKS
3 weeks on, 1 week off
PLAN ENDS WITH
Event day
SPECIAL NOTES
This plan contains a mix of indoor and outdoor rides, with the longest sessions being outdoors and occurring over the weekend as long as you select a Sunday as the end date.
All Purpose Road
GOAL
To improve overall bike fitness with indoor only sessions
BEST FOR
Riders with at least three hours of riding a week for the previous 2 months and 3-6 hrs/wk available to train
TRAINING BLOCKS
2 weeks on, 1 week off
PLAN ENDS WITH
Full Frontal (Fitness Test)
SPECIAL NOTES
All rides are scheduled to be completed indoors, with the longest sessions occurring over the weekend (assuming a Monday start date or Sunday end date).
The all purpose is a great place to improve your consistency in training and general fitness whereas the century and GF plans have more specific outcomes. I would do the GF plan closest to your event.