Each course is unique, and with that comes unique organization requirements! Consider how often your students will be using the LMS, as well as the types of information or assignments you'd like to use. Using Modules or Weeks allows students to track their course progress and ensure they're accomplishing tasks in the correct order and at the correct times! Long lists of assignments and links will lose students.
Some courses do better being organized by topic, subject or concept. Other courses benefit from using textbook chapters, weeks or other types of organization.
No! As long as your are consistent from start to finish, the decision is yours! Some professors find it easier to divide content by weeks to help students keep track. If your content doesn't follow a weekly chapter or subject, you could consider using modules which have the option to span more than one week.
Units are larger than Modules or Weeks.
Collapsible sections titled by Module and/or lesson topic
Typically 1 module = 1 week, but option to span multiple weeks! (consider using Units if using larger chunks)
Collapsible sections typically titled by Week or Week/Dates
Avoid starting new topics/chapters mid-week
Units can be formatted in many ways!
Units may contain several weeks/modules
Handy for 15-week and F2F courses that don't use the LMS as often.