Microwave engineering is its own field of study. Various PCB features can act as resonators and/or antennas, the choice of dielectric itself can have a large impact on performance, and characteristic impedance becomes a critical concept.
So long as you can keep all of your trace lengths electrically short (smaller than one fifth of a wavelength), you should be OK with basic rules of thumb. Otherwise... you'll need to to quite a bit of study first!
The no ground plane on top is one type of waveguide, with a ground plane on top it becomes another, and removing the bottom ground plane gives yet another type. You'll need to know what these are -- check out the terminology for microstripline, coplanar waveguide, and conductor-backed coplanar waveguide.