Does parasitic capacitance of a microstrip trace add to the value of a physical capacitor on the same trace?
If one sees it as a series element, then it would seriously reduce the value of all capacitors that has a bigger capacitance value than the trace. If one sees it a parallel element, then the trace capacitance would add to the value of the capacitor. I guess the latter must be right, but I'd really like to get some opinions on how this works.
The same goes for inductors.
Parasitic capacitance absolutely adds to the value of a physical capacitor on the same trace (same goes for inductors and resistors!).
In a microstrip the parasitic capacitance is to the shield layer (typically ground). So that would be a parallel capacitor and would add.
Likewise, the inductance is due to the trace itself (self-inductance) and also might have some mutual with other traces. It is a series component that adds to the inductance of the trace.
A good rule-of-thumb if you're confused is that parasitics on a signal trace will make matters worse, whether for capacitance, resistance, or inductance.
