1) Hide placeholders of blocked elements
If unchecked you will see blank spaces where ads or other blocked content would have been. I leave it unchecked in order to maintain page layout. It does not make any functional difference.
2) Show the number of blocked requests on the icon
I check that just to get a sense of how "blocked" any given page is. Eg., if some function of the site is not working and the number of blocked items is large, I might presume the lack of function to be attributable to a blocked script.
This very page at BITOG indicates "7" elements are blocked for me.
3) Make use of context menu where appropriate
I check this so when there is something on a page that I want blocked I can simply right click that element and block it.
I leave unchecked for the once in a blue moon I care about the content of a tooltip. Tooltips are really not invasive.
I leave unchecked to maintain the site's aesthetic intention.
6) Enable cloud storage support
This will back up your settings to a cloud storage account. I don't bother.
7) Disable pre-fetching (to prevent any connection for blocked network requests)
I leave this unchecked because pre-fetching data can speed up navigation sometimes. Having a site that knows who you are pre-fetching data may avail some of your information to the parties from whom the data is being fetched, however.
8) Disable hyperlink auditing Prevent WebRTC from leaking local IP addresses Block CSP reports Default behavior
I check this; as someone who from time to time has to be intentionally vague about my whereabouts in order to gain access to U.S.-only content.
9) These default behaviors can be overridden on a per-site basis
This is probably harmless to check and one day you may want to treat one site differently than some others.
10) Disable cosmetic filtering
I am a web developer and it irks me that people can mess with my layouts and designs. This really does not play into privacy but *might* save you some bandwidth; with bandwidth being the last thing most people in the industrialized world ever have to worry about.
11) Block Media Elements larger than 40kb
Again, mostly to save bandwidth. I would expect a majority of these elements to be media.
Remote fonts do not take up much bandwidth and present zero security or privacy risk. If anyone chose to use a remote font it is because they feel that font is integral to the look-and-feel of their site. I like to respect that.
I don't check this. https://www.ghacks.net/2017/10/19/ublock-criticized-for-blocking-csp/