Welcome to the forum. For starting out, may I suggest looking into the shorter products: F3 or GP38 locomotives and 40 ft boxcars, hoppers and such. The briefcase layouts have the tighter curves and some of the larger rolling stock may not play well.
My only Z scale unit so far, is a Marklin F3 SP Daylight and its passenger cars from the 1980's. You're absolutely correct Mark, for the longer passenger cars do not like the tighter radius of the inside loop, but run well on the outside loop of the "Meran" briefcase layout. I'm considering the AZL WP GP7, WP 40'AAR Boxcar 4-car set and a WP Caboose, for the inside loop.