That really depends on what you want Adguard to do. If it's just ad filtering then default is enough, although I normally increase how often it checks for filter updates. If you want it to help in privacy as well then activate stealth mode. It will automatically activate filters for other languages if you visit any site with a language it has a filter for.
The main advantage of Adguard (Desktop) is that he remove the ads before the page is loaded, so no silly white empty square in the middle of the page, and it is system wide so no need addong extensions on every browser you use.
FYI, AdGuard is working on DNS component for its desktop version, which will feature secure DNS and DNS filter, just like in Android version. ETA unknown, but it's work-in-progress.
You can use currently available free tools such as Simple DNScrypt and hosts file to achieve the same, but it's good to have all combined under 1 roof.