Tachi, wareware and fun

Hello! I would like to ask about a few sentences because I am not sure if I understand them correctly.

-tachi
I understand that this word means "we" "us" and we can translate it as "me and all the rest (of the group)". However, for example, if a young girl is standing in a mixed group (girls and boys), is it correct to use "atashi tachi" or rather "watashi tachi"? After all, there are also boys in the group, not just girls.

- wareware - I've read that this is a rarely used phrase and is used more in very formal meetings. However, if someone uses the phrase "wareware" when talking to a group of co-workers - does it mean that this person keeps his colleagues at a distance? He doesn't see them as colleagues and treats them only as co-workers?

フン - do we classify this word as rough? (I'm thinking of a situation where we don't like something and get irritated)

I will be grateful for your help!

-tachi
I understand that this word means "we" "us" and we can translate it as "me and all the rest (of the group)".

I'm afraid you're wrong. "-tachi" is a suffix to show that a noun (basically living creatures) is plural form. Let me show you some examples:

watashi/atashi: I/me
watashi-tachi/atashi-tachi: we/us
otoko: man
otoko-tachi: men
inu: dog
inu-tachi: dogs
Mary: Mary
Mary-tachi: Mary and the others

- wareware - I've read that this is a rarely used phrase

Not really. But it's a phrase used more among adults rather than children. If a little child says "wareware", the child is pretending to be some kind of a big shot.

if someone uses the phrase "wareware" when talking to a group of co-workers - does it mean that this person keeps his colleagues at a distance?

Not at all. It's just another way of saying "we/us". But you can say that it's not particularly a lady-like expression. It's uni-sex or mannish.

フン - do we classify this word as rough?

I'm sure you're looking at some kind of a writing, because people don't really say フン in that context. But, like you suggested, it means "hmph". And, well, could you openly show your irritation and not sound rough? I can't.

I hope it helps.

Thank you very much!
I'm sure you're looking at some kind of a writing
It's true. This word appeared in the text and aroused my curiosity.

atashi is not used by adults. one of toddler words

atashi is not used by adults. one of toddler words
As far as I know, "atashi" is mainly used by young girls (teens and 20-somethings). Women 30 + are unlikely to use this phrase.

I personally know no one who orally says "watashi" on a daily basis. I and every woman I usually meet always have used "atashi" (if not "atakushi") ever since I can remember. And I'm 62. In fact, I'm listening to adult women using "atashi" on podcast this very minute.

Here is an example:
https://www.youtube.com/watch?v=MhG1_EO4oKs

Btw, children today tend to use "uchi" or call refer to themselves by their names such as Hanako or Mary.

Uco, to tell you the truth, everything you say is new to me, as I get my knowledge of the language mainly from the Internet and textbooks. Until today I was convinced that "atashi" is used only by young girls, while adult women mainly use "watashi". However, as I mentioned, I have textbook/internet knowledge, so thank you for making me realize that in reality there are slightly different rules when it comes to using this type of sentence.

You should try watching non-fiction documentaries and talk show videos.

I think any girls in elementary school don't say themselves as "atashi" in front of teachers. probably, atashi, atai is local words in Tokyo area. there is a 漫画, あたしンち. Tokyo local story.

I think "uchi "( woman's word) is Osaka local word especially used by old women. there was a catchphrase of かしまし娘. うちら陽気なかしまし娘. but, not be used recently. ("uchi" is the word used in the age of かしまし娘.) I don't think it is common in Tokyo area historically.