I prefer searching for settings with “English” as my interface language because then I can search the names of the settings, which are always in English, and the descriptions at the same time. Sometimes the keyword I am looking for is only in one of them, and then a German description makes things more complicated.
Apart from searching settings, I try to use the interface in German. That helps with improving the translations and noticing bugs that occur only when your interface language is not English.
It’s also helpful because some things, like the “about the category” topics or placeholders you use in messages sent by the automation plugin, usually use the interface language you used at that time. Also, site texts you customize default to your interface language.
So, in general, I use the default locale of my forum (German) also as my interface locale, but I change it to find settings. I have a theme component that adds a toggle button to my sidebar so I can change my interface language with one click.