This is the topic I know the most about and will have the most to add to, but I'll try to keep it short for now.
Many US states have already dabbled in criminalizing supporting trans kids and making schools, doctors, etc. mandatory reporters of gender nonconforming behavior to the state, for child protective services to follow up on and remove children from parents. It's not hypothetical. Those details haven't been mentioned explicitly in the EOs yet but we can expect a resurgence of this kind of thing.
Halting federal funding for trans care means Medicare won't cover it, and removal of LGBTQ identities from protected class status means insurers can stop covering it, which potentially leaves the vast majority of the US population unable to access any trans care legally. (Context for non-USians: we can't afford anything without insurance and even then it's a gamble, and a single hospital stay can easily push you into bankruptcy.)
It's important to note here that "trans care" doesn't just mean starting transition but continuing the hormones a person will usually take for the rest of their life. If you've had your hormone-producing organs removed (and that's a true if, because it's not a uniform thing that everyone does), that's necessary for preventing osteoperosis and various other ills. The human body isn't meant to function without any hormones -- they do a lot beyond sex stuff! If you aren't producing them and aren't getting them externally, you go through menopause. Trans care could also mean cancer screening or treatment (e.g. prostate for trans women or ovarian for trans men). Again, not hypothetical: insurers have routinely denied these things for trans people until their hands were forced by state or federal law.