I firmly believe that people who believe they are trans do so because they genuinely feel more at home behaving and looking the way that society deems "masculine" or "feminine". Gender is a load of old bollocks because it's a social construct- it's made up. No-one's sex should be associated with defined behaviour or appearance- a masculine or feminine stereotype. You don't wear skirts and act submissive because you're a girl biologically; you've been socially conditioned to look and act that way and you have always felt comfortable doing so. Men don't act dominant, repress their feelings and wear their hair short because of their biology; they've been socially conditioned to look and act that way and feel comfortable doing that. They've been told, from a baby that that's what it means to be the sex they are. But it isn't real. "gender" is something that changes and can be completely different in one culture to another.
The real problem is conflating sex with "gender"- being brought up from a baby with a defined "gender" - being told they have to look/dress/behave a certain way because of their biology. If any child decides that they don't like that "gender" - "actually I have a willy, but like playing dolls with the girls, wearing dresses and having my hair long" all hell breaks loose. They are punished, told they are wrong, teased and rejected. And there is the problem- adults' anger, inflexibility and extreme reaction and non-acceptance. I'm pretty sure the "trans" identity has been created as a backlash in order for the vulnerable majority to try and find a way to be accepted for who they want to be.
A small minority of male sex fetishists and perverts have latched on to this as a way of being able to abuse.
I liked climbing trees, doing bike stunts and playing football with the boys as a child. I hated dresses and long hair. I liked wearing dungarees. Never acted "ladylike". Was always covered in mud and wanted to be Spiderman or a car mechanic when I grew up. I wanted a Fisher Price car garage or a Skalextric for Christmas. Never got one. Was not allowed. Because I was a girl. I got bought Barbies and Tiny Tears and dresses. I was called a "tomboy". These days I might have been diagnosed as transmale. The problem with that is that I'm a straight, cis woman; albeit one who hates pink and like a pint of Guinness.
Because of the aforementioned minority of abusers mentioned earlier; instead of looking at our own cruel behaviour towards people who don't want to look and act a pre-defined way; we are getting reactive and angry; reinforcing those strict gender stereotypes with our kids constantly and blaming those who feel that way for it. We want biological sex to be defined and encoded in law. We want to restrict people's rights because of it. This not only affects "trans" people, but also those 1.7% of the population who are biologically intersex.
Men are the main perpetrators of violence - whether that is towards men or women. That's not biology that's caused that- that's gender stereotypes. Sports are gendered- even chess and shooting. That's gender stereotypes. Patriarchy and misogyny is the product of strict gendered society and upbringing.
There are some things that need to be based on biology- illness, medical treatment and research, safety features based on physiological attributes, and to a certain extent- sports that rely on physical strength and endurance (although there should be some way of putting those sports into "classes" based on physical attributes in order to not exclude those who are biologically intersex, or people like Castor Semenya who is biologically cis female with abnormal testosterone).
Refuges should be sex-based. Prisons should be sex-based. Bathrooms, baby and child rooms and changing rooms should be gender-neutral single, lockable cubicles. Schools should be teaching that children are children and not teaching "gender" or social stereotypes.
Otherwise, I believe the trans ideology will become the only "safe" or "accepted" way that people can be who they feel they are and it will only become bigger, more extreme and more vocal; leading to more stupid things like what OP saw on TikTok being posted. Yes, female hormones do have side effects on men- including on their moods, breasts and on their bowels which can come and go. No, it cannot make you experience periods.