Posting limitations are based on the type of subscription you have on Twitter / X. If you go over you will be prevented from posting and scheduling. You can tell if you have a premium account as it will show in Typefully like this:
Premium Users
If you're an X Premium user, you can publish up to 50 long form posts in a thread, each with 25,000 characters per post.
If you want to include formatting, you will need to post directly to Twitter / X.
Non-Premium / Free users
Free Twitter / X users can publish up to 50 posts in a thread with up to 280 characters per post.