When we are talking about RF in general I think it is important to understand that RF technologies may vary dramatically with range of frequencies.
1. Everything from 100kHz to 300MHz. Coils, RF transformers, regular MOSFET devices used in many designs.
2. Everything from 300MHz to 4GHz, microstrips are used and have reasonable sizes, using RF substrates (Rogers 4004 etc...) is beneficial
3. Everything from 4GHz - 25GHZ and up, RF substrates are must, microstrips, wave guides, exotic components ...