Hi Julie!
We have the same issues with setting up registration. I created a votable thread about alot of this here (back in 2017): Additional Attribute Features/Support for Complex Courses
I have one course which is a standard conference with 20 workshops all of which have fees. They HAVE to be capped so I’ve been forced to use a regular course page for the standard conference fees and then another course page where all 20 workshops are child courses. With this method, I’ve been able to cap workshops and also accommodate workshop changes. But it’s alot of a manual work since I’m manually changing orders and making sure enrollments are updated when those changes have to be made.
I also had to modify the course marketing feature in order for the ordering process to make sense. Users would sign up for the main conference and at checkout they would see the workshop page.
It’s quite a bit of off-label use and manual work, but it’s the only solution I’ve found to provide the kind of flexibility I think you’re looking for. If you come across a better solution though or advice on doing this kind of thing better I’d also love to know!