Voice resonance has more to do with your body/skull structure than anything. One thing that I find interesting is that most phenomenonal singers have rather large mouths. My singing ability actually improved as a child after getting my jaw expanded.

You can kinda test this out yourself. Hold a note with your arms by your side, then again with your hands on top of your head with elbows out. Your voice will have a lot more resonance because you’re expanding your chest (this is also the best position to catch your breath in)

Source: classically trained musician taught by PhDs in the various instruments I can play (including singing)

I also have a fun breathing exercise that will make you super light headed, which is fun.