The Harz layout is flat, indoors, with relatively clean track, and maintained stock..
We draw about 4.2Amps with a dozen loco's sitting with lights and sound, 8-ish 4-way point decoders, turntable, two (sometimes three) loco's running at once.
Visiting loco's quite often 'fizz' and spark on point-frogs, but unless running very slowly, do not cause the CS to shutdown. - Set at 7Amp limit.
These are mostly LGB loco's, of course.