"Choose your own adventure" sounds like a lot of fun for your students, @RebeccaKranitz. I'm not familiar with Moodle so don't know what a Moodle module can contain, but within Canvas terms I'll assume that students will complete a module through some type of assessment. 

To me the easiest way to achieve your interests would be to create an assignment group with your 10 optional modules and set it up so the lowest 5 scores are dropped. Students would then choose the 5 that interest them. If there is content you only want students to see after they select a certain path, you could link that content from the assignment. Otherwise you could share the content for all 10 optional assignments and allow students to view the content before they complete the assessment. There is a Canvas guide that can help with this: How do I create rules for an assignment group? 

Another option is to use mastery paths, which would work best if your 10 optional assignments are split into 5 pairs. With mastery paths, how a student scores on an assignment (I would use a quiz in your example) gives them access to certain other Canvas items (content, other assignments, etc.). That would take some deliberate planning and starts with another document in the Canvas guides: How do I use Mastery Paths in course modules? 

There is another option that will hopefully be coming soon, and that is to limit an assignment to a particular group. How this could work is your students would choose which groups they join and thereby be assigned the particular tasks. Assignments can already be limited to individuals and sections, but the idea to limit them to groups is among the ideas in a theme that was prioritized for development earlier this year: Enable Differentiated Learning at Scale. 

I’m going to mark my response as a solution, but there can be more than one. I hope our colleagues here in the Community can share other options for getting this important information to teachers inside Canvas.