Many add just don’t show up. The reserved space stays white. Also, depending on the aggressiveness of your block list, some pages don’t resolve (just like they never existed). E.g when you click on adds in a google search result, it leads to nowhere.
Short outtakes make no difference. It is your primary source for matching names to IPs. Depending on your configuration you can have alternative sources.
SSUPII@sopuli.xyz 3 days ago
If the ad is under a filtered domain, it will simply not load. If the ad is under the same domain as the site you are using (ex. Youtube) they will load just fine.
When the primary DNS is down, the secondary DNS will be used. This is the same regardless if PiHole is used or not, but is how DNS works.