I'm not the most knowledgable on this, so take what I say with a grain of salt.

What should be the most important is how you yourself feel, and then labels should come with that, and not the other way around: you shouldn't "choose" to identify as demiboy, and then try to change how you act and behave to try and match what's on the label.

The fun in labels and the such is that you can interpret them as you want (for yourself)! You can say you identify as demiboy and mean with that 100 boy, 50 girl or 100 boy, 23 girl or even 100 boy, 75 girl and none of those are more correct or a better fit to the demiboy label: it all comes down to what you decide "demiboy" means to you (also this applies to any other gender you might identify as, I'm just picking demiboy as an example as it's a bit more specific).

Also, you can always change your mind after choosing a label, it isn't set in stone so another option you have is to just pick one and roll with it, find out how it feels and how YOU feel about it, and if you don't like it then pick something else and try that!

I hope this makes some sense and is maybe helpful. Good luck on your discovery journey !