Kamen Rider have 3 different type of movies... Crossover, Summer and Return movies.

But unlike their Sentai counterparts, their movies can be range from Canon to Non-Canon AKA Alternate Timeline, especially in early day of Heisei Kamen Rider.

Den-O, Decade, Double, Fourze, Wizard, Gaim, Drive, Ghost, Ex-Aid, Build, Zero-One, Saber, Revive and recently Geats' Summer movies are Canon to the story while Agito, Ryuki, Faiz, Blade, Hibiki, Kabuto, Kiva, OOO and Zi-O's Summer movies are Non-Canon as those movies take place in alternate timeline.

So do you prefer the movies to be canon or non-canon if you were to tackle movies for your Kamen Rider fanfic?

7968963
Depends on the movie and how well it can work in the season's main timeline but if it has characters or elements i really enjoyed or want to use id try to incorporate them

7968963
Canon.