Travel / Few questions - Canadian-born travelling to Poland in less than a week [9]

Czesc :)
I am an 18 year old Polish girl born in Canada - I speak the language fairly well and on a daily basis so I have no problems with it. I've been to Poland several times as a child but haven't been there in about 10 years. I also have family all over that I will be visiting and I have a good contact with them. I will be mostly in Warsaw, probably spending 4-5 weeks there with my cousin.

Just a few questions out of curiousity -

I have heard it is unsafe to take a train in Poland - is this true?

How do Polish people view Canadians as? I won't be walking around wearing a big Canadian flag as I will just relax and not look "touristy" in general, but this is just a question out of curiousity.

What should I NOT carry around with me?

What kind of ID is considered "valid" in places such as nightclubs? I have a BC (Canadian) driver's license but I'm not sure how "good" it will be. I'm just a bit nervous about carrying my passport around. I also have an ISIC card but I know it's not really used for valid age confirmation.

Any other tips?

Dziekuje :)