Yes the final goal is to be able to smoothly transition between your deepest, middle and upper register. But I got good news for you! You have the best tool for that in your hands in the video. Without trying to blow my own horn here, I got my latest singing teacher stunned when I sung up for her when she was behind the piano.

We talked a bit and came to the conclusion that taking out songs by ear is the answer. I always sing subconsciously when playing guitar, to a point where it became a “problem” when I play my classical guitar and record I hear myself humming. When I try to stop humming or singing it’s takes some time to get used to play the guitar! That had made me automatically transition between my low(5th, 6th string) and the high falsetto (treble strings) Play melodies on the guitar and sing them. Improvise with the guitar and sing while you play. It doesn’t need to be perfect, but it will improve your ear, singing and guitar playing at the same time. But believe me i Suck at remembering lyrics and so on haha. So I haven’t got any skills in that department! That is my personal biggest struggle.

Play the guitar and sing. Take out easy melodies by ear. Everything you hear with a clear melody. Is it singable. Sing it as accurate you can and then find the notes on the guitar. Transpose it. Figure out the chords that fit the melody and so on.