this opera singer and teacher just put out this video and he mentions doing the mickey mouse voice he talks about falsetto and head voice and how to get a full voiced sound in falsetto and such in m2 (he doesn't say m2 but he is talking about notes and sounds in that register). specifically between 33:06-36:10, that is incredibly helpful for demonstrating and finding that your full voiced m2 tone comes from falsetto, all you're doing is as he says increasing the velocity of the air, the volume which then creates the full voiced "chest" like quality. and this guy is singing powerful loud operatic style singing yet in that time frame you can hear, as he softens the volume and lowers the velocity, its just falsetto!! also he focuses on opera but the principles apply to all styles of singing not just opera

https://youtu.be/8e4EVgUmLXI?si=ef9TsTFCfUlAAlRq