Hey! I have a few…

Hey! I have a few questions that doesn’t pertain to blogging per se, but writing and I know a lot of you are fiction writers as well.
I’m a skinny, straight white female writing/editing my first novel(!) and I’m hoping y’all can help me with my diverse characters because I’d hate to inadvertently say something offensive or politically incorrect when describing them.

One character is a curvier girl. I don’t love the word ‘curvy’ because I find that too sexual and this character is seventeen. How else can I tell readers she’s not skinny? And I don’t mean like…obese, I just mean, not super skinny.
Another character is black (but is saying ‘she is black’ okay?). In my head she’s a lighter shade (think Beyoncé) but I don’t know if there are words to describe that either (that I, a white person, can use).

Another question I have is if anyone has tips for writing accents (Irish and/or Australian, specifically) or if it’s better to just write the dialogue normally and let people do their own accents in their head when reading.

Any advice or guidance or links or tips would be greatly appreciated. Thank you!