Hi there,
Greetings!
My response to your questions:
1. Yes, PS and CSOM can be used to setup site theming at a site collection level, and can be used to disable existing themes. With the introduction of modern pages, this theming would be the way forward. Have not personally used this feature and hence not able to provide an exact limitation of this feature.
2. Yes, SPO analytics can be retrieved using PS. I believe the 'Analysis Engine' is core that needs to be enabled in PS. Analytics require usage logging to be enabled before we can retrieve any kind of reports. You can retrieve the number of page views, Top pages, top visitors, number of referrers, number of unique visitors, top browsers.
3. By SharePoint view retrieves all items in a library but limits the display to 5000 records since this is the threshold set internally to minimize the query response time. To overcome, the best practise is to setup metadata and indexing so that when we retrieve documents / items, the server already has information about the file / document being retrieved, hence making the process more efficient.
My experience with SharePoint
- Have used MS Graph to integrate with Web app / portal connected to Dynamics 365 Sales (CRM).
- Have setup SharePoint DMS on Dynamics 365
-Have used CSOM / JSOM / REST API extensively in SharePoint Add-ins, Web apps, portals
-PS - mainly used for administrative purpose during deployment
Running out of space to write more... look forward to your connect. thanks