I personally see all this mostly from the other side, that is, the execution side, not the construction side.
But there are certain basic requirements, which surely are not set too high. But then I suppose construction, use, and placement might require higher standards and class in some cases, I assume.
But generally speaking, there aren't particularly hazardous requirements for garages and other smaller standalone buildings in one floor. If a garage is built together with the house, they should as a rule (always!?) be separate fire compartments, and the requirement usually never exceeds more than EI30, possibly EI60 if the fire department has a long response time ...? for these smaller simpler buildings?
I'm using a lot of question marks for a reason here.

I don't have a very good grasp.
I did some research on fire classes, response times, and execution requirements when I was building, but they were simple constructions.
In my work, I usually have a solid understanding of fire protection boundaries and which EI class should be met, as I connect a lot of fire dampers, make penetrations in walls and floors, etc., in larger properties.