How do pilots do a preflight inspection of tail-mounted engines?
In personal experience, I often look for a step ladder to inspect ground inaccessible engines and control surfaces and I have seen others look at their aircraft from a second story window.

My personal practice is to walk around the aircraft prior to every flight, not just at the first flight of the day, but I often had to make time for that. It may not be common practice. But that is an aside.

Here's the reality. If you are talking about the walk-around that the pilot or flight engineer might do, there are not up close inspections of the elevated engines and control surfaces. The walk-around will look for leaking oil, missing $1500 fasteners or whatever, but one is not checking the dipstick prior to engine start.

How are things inspected?  The manufacturer factors that into the design.

From an operational standpoint, the pilot(s), FE will look at performance during engine start, and make sure that the profile does not deviate from the expected temps, flow, etc.

In summary, if you can't get to it, it is not likely on the walk-around checklist.

Addendum.  At least one company is seeking FAA approval to utilize drones in aircraft maintenance inspection (not pre-flight) processes, which would reduce the cost and risks associated with scaffolding and lifts. As part of their application to FAA, there will be demonstration periods where aircraft are inspected with both methods, and results are shared with the FAA.