is there any way to cache network content and management well by the cache system
You can add them to reading list and have them offline.

https://support.apple.com/guide/safari/keep-a-reading-list-sfri35905/12.0/mac/10.14


  


It gets tricker to work if it is synced across devices. So I tend to save pages I need using File menu > Export as PDF.. or Save as.. > Web Archive. 

Often wget -c site.com is also helpful.

As pointed out by nohillside in comments, youtube-dl can save videos offline too, not just from YouTube, despite its name.

Both of the CLI tools can be managed by brew, cleanly.


https://brew.sh