need some rss feeds to display different # of posts

my blog is set to display ten posts per feed, But i have some categories that i want feed to display different numbers of posts. im looking for an easy yet proven edit to control the number of post that can be displayed by rss feed of specific categories. these rss feeds will be from my blog & displayed on my website. if no edits are available would settle for info on plug in, all help is welcome

my blog > https://psychic3000.com/wordpress/
my website > https://www.psychic3000.com/index.html