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Start looking for YouTube videos with Eric Bogatin. He is a professor at CSU Boulder and has re-written the book on proper PCB design. (He does have a book, but he debunked a ton of old theories on high frequency board design and signal integrity.) If there is anything you must do, is follow his work on ground and power plane design or anyone that references his work. If someone uses a ground plane to just "fill in gaps" or have it act as a generic fix-all "shield", ignore them. (Many RF/HF myths came from the way boards were fabricated, not because of a specific circuit function.)

Once your signals get past a certain speed, you need to learn how electricity actually flows while understanding that both AC and DC theory applies. If you didn't know that energy flows in the field around a wire, you probably need to step back a little before you step forward. (Reference Veritasium on YouTube: The Big Misconception About Electricity )

You don't really need to get into heavy RF theory, but it helps. If there is anything you must learn about, it's impedance matching and why it matters. To summarize quickly, if there is an impedance mismatch between your transmitter and your antenna, you could easily blow out your transmitter due to excessive power draw and signal reflection. (That is somewhat rare for low power devices, but not uncommon once you start to transmit above 5-10 watts.) If a device needs an antenna, use it, even if were are talking about something as common as WiFi.

For your first designs, respect trace lengths and recommended components. Most of all, respect the keep out areas around an antenna diagram and ensure your ground plane is properly designed and away from the antenna. There are many shitty designs that do work, but you want to strive for precision for your first few iterations.

Also, decoupling becomes more than just a thing to do that might improve stability of your MCU or other components. It's entirely possible to get the rest of your PCB resonating which will cause all kinds of noise. This is partially negated with proper decoupling.

High frequency design just takes a little more care. Just remember the basic saying: Everything is a resistor, capacitor and inductor.

Now, if you just work with modules (and ESP32 with an integrated antenna comes to mind), almost all of the hard work is done. Make sure you have proper clearances, slap the thing on a board and you are good to go.

For the absolute basics, impedance matching with proper antenna length is what you need to learn first. (Receivers are much more forgiving than transmitters, btw.)

I am fully aware that some key details are missing here and just summarized as best as I could. If something I said turns out to be misleading, that isn't the intent and I apologize in advance. The intent was just to kick start more curiosity.

Edit: RF design and high frequency board design share some design considerations. Not all signals on an RF project are going to be high frequency and not all high frequency designs use RF, but, all high frequency designs can quickly become RF designs.

Also edited a time or two for clarification, grammar and spelling.