One of the things that has changed significantly since 1.9 is the way that courses manage enrollment. Rather than configuring price or meta courses in the course settings, Paypal enrollment and Meta Links both find a new home under enrollment methods in the course settings block.
For Paypal, the process remains the same (you can set global defaults at the system level but then override each at the course level where applicable). One added feature is the ability to define start and end dates (duration remains a setting option) for enrollments via Paypal which might be handy if you want to specify the dates between which students can self-enroll.
For Meta courses, there’s a name change (this is now Meta Links) but the process remains. If you want students to enroll in X course but by default get access to Y (you can also set it up for students enrolling in both X and Z get access to a shared Y course leveraging a one to many approach) you’ll need to go to the Parent course first (this is where students will be enrolled by default, but the course itself is not enrollable) and add a “Course meta link”.
Both function exactly as they did in 1.9 with just slightly changed location for the settings.