As far as the phrase " Pregnant People" it does sound weird when you say it aloud. Its too illliteritive. Why not just Pregnant if theres a need to generalize or pregnant individuals?

I dont see how that sounds weird. If you don't like the illiteration, you can replace it with another noun. Pregnant is an adjective afaik, so it needs a noun to be applied to. Of course language can change, but expecting vitamin manufactured to be the ones to change the part of speech of a word seems like getting the order backwards.

I feel that its just as easy to actually ASK the person in front of you what term they prefer you use and then just use that term rather than try and generalize and lump everyone together.

So vitamins aimed at pregnants (guess we are making it a noun now?) will have a person behind the table that asks what noun you want written on the bottle before they hand it to you?

This isn't about individuals: it's a mass produced product. Of course for individuals you can tailor the language to the individual. I don't see why you would normal ask anyways: most of the time you'll just be implying someone doesn't pass, whether they're cis or trans and if they're trans and not comfortable coming out yet, then you may be putting someone is an uncomfortable position of choosing to come out or misgender themselves.

As a cis women i wouldn't care to be referred to as a pregnant person but it would've really bother me enough for me to correct them. If they called me a pregnant man, I wouldn't get all offended and think they hate all cis women, id just laugh and correct them

Seems like reasonable responses. I'd be confused why calling you a "person" would be incorrect, but I'd try to respect it, but I'd eventually conclude you are probably transphobic.

I present as a guy and my body is masculine, so people gender me that way. It's not really a big deal imo - like there's certain specific terms like "man" that are kinda icky, but I'm not gonna care at all if you say "he."

But that's just my own experience. Different people are going to be different. Still, at least most trans people I know don't get mad at people for misgendering them, even if they have their pronouns on their shirt or the people misgendering them have been corrected many times and are just intentionally being disrespectful. Of course some of the times, those interactions may make someone's day much worse even if they don't show it at the time.

Cis people get the advantage of cis-by-default treatment. Of course trans people are going to be less secure in their gender on average given all of the transphobia in society. Even if a cis person is regularly misgendered, they can still easily feel secure in their gender simply because they of the way they were born. That same source of confidence for cis people is an obstacle to be overcome by trans people.