Post_Event_List vs. Post_Page_Event

They are very different things, although they both use the word "event".

The event string in event_list and post_event_list contains a comma-delimited list of events (counters), which may have a value and/or a unique ID. For example, if you used custom event1 for registration and someone triggered that action by registering, it would appear in this list. Look for event_list in this documentation: https://experienceleague.adobe.com/docs/analytics/export/analytics-data-feed/data-feed-contents/datafeeds-reference.html?lang=en

post_page _event shows the type of a hit based on the page_event value. This is the table in the link you provided. These are types of Adobe calls, e.g. a custom link type call or a page type call. In the event1 example, event1 could be set in either a page type call or a custom link type call, depending on your implementation needs.