Override DNS setting is generally not necessary.
This is because (1) generally no one set up custom dns on their device. (2) if some one set up custom dns 8.8.8.8 on windows, it is automatically encrypted. The “override” option on the router does not work with encryped dns.
Of course if some one set up custom dns which is not encrypted (e.g. in old version of Windows), setting Override option is necessary.