Uhm, well a head voice does indeed tend to sound less natural than a chest voice, since it's the voice that you'll generally sing with. But then again it's not so bad. A head voice is what most women (most people?) will use when speaking to someone they're not familiar with and want to make a good impression on. When doing a job search call for example you can be sure I'll be mostly using my head voice.
Basically, the way I understand it, there are three kinds of voices: the chest voice, which is the relaxed voice that most people will speak with most of the time; the head voice, which is a clearer kind of voice that resonates elsewhere, less deeply, used for when more clarity or precision is desired; and the falsetto, which has some volume but basically no resonance at all, and can be stretched downwards and modified to sound more natural, but mostly will always remain what it is: basically only useful for screams and funny imitations, and, if trained especially, for singing (think surprising opera feats and YouTube video of a man singing Celine Dion very well). But it will always remain ill-suited for speaking, I think, because no matter how much strength and depth you manage to add to it, its very nature is to lack resonance, and resonance is important in natural speaking. You can try to camouflage its lack of resonance by dimming its volume so that it loses its distinctive Mickey Mouse feeling, but but that's about all.
A head voice is less casual and natural than a chest voice, but contrary to falsetto, it can be and is used for speech.
So, for the resonance... yes, there are two kinds of resonances. They roughly fit with the voice types, but not fully, I think. While the chest voice is mostly called that because it feels like it comes from the chest, it can sort of integrate head resonance as well; vice versa for head voice. Chest resonance is how your chest vibrates and you feel like your sound is resonating and getting its depth and strength below your throat. Head resonance is weaker, but it feels like the voice resonates in or above your throat. They overlap and mix somewhat, but mostly head voice is head resonance and chest voice is chest resonance.
So uhm, if you make a sound that's gradually higher from your lowest possible note, with your hand on your chest, normally (hopefully) at some point you'll feel your chest resonate noticeably less. There's a chance that at that point your voice will hit a "break" and you'll need to interrupt the sound, reajust your vocal cords and start again. At that point you'll be hitting your head voice.
Thing is, even though for a maximum natural feeling having a passing chest voice is best, not all trans women can do that. And actually, some natal women will communicate mostly with their head voice, even with their friends, and it's not the end of the world. So you should concentrate on getting a passable head voice, and then consider trying to get a more natural, passable chest voice.
You should also note that by going down from a falsetto, what you end up with is either a modified falsetto (which I feel is what you have), either with a head voice that you slipped into by sliding down. Either way none of those is a chest voice (your chest voice is the lowest of the three, and even though there's overlap, it just doesn't make sense that you'd start from falsetto, the very extreme upper limit, and reach chest voice.
