Played on intensity 23. The game tracked 36 hours of exercise but I estimate the time I spend exercising in Adventure mode to be easily more than 50 hours.
For our US citizens: The 105 km distance are around 65 miles or 62k smoots or 2e¹³ beard-seconds or whatever units you guys are using.
Didn't farm XP or repeated worlds, finished every stage on the first try. Only repeated a handful minigames for 100% sidequests.
NG+ Stuff:
NG+ continues the story in a world where you have defeated Dragaux and NPCs do recognize you again. You play a different variation of the original story.
You don't have to finish the adventure mode on 100% before you enter NG+. You can switch between normal mode and NG+ anytime in the navigation menu.
You keep your character and all of your stats. NG+ is called "Extra Fitness"instead of a new game mode.
First level on NG+ isn't called 1+ or something but "Chapter 24 Extra Fitness Lvl. 181", so they simply keep counting but the worlds have their own power levels.
It also seems like there are no seperated sidequests anymore but the quests are integrated into the normal missions as additional win conditions.
You keep unlocking new clothes, recipes and levels of the exercises.