What is the best way to transfer files from old macbook to new macbook?

Hi all,

I should be receiving my new 16" MacBook Pro in the next 1-3 weeks. I am currently using a MacBook Pro that I've had for 10 years so it's been a while since I've transferred files from one to another. This might be a silly question but what is the best way to do this? Most of my MS Office files and photos are on a server already and won't need transferred. I know about Migration Assistant but what exactly does it transfer? I don't want to transfer all the "junk" that's accumulated after using this machine for 10 years. I would like to start mostly fresh but certain things would be helpful to have on the new MacBook, like iMessage files, internet browser bookmarks and saved passwords, etc.

Also, once everything is transferred over, how do I erase everything from the old MacBook in order to sell it?

Thank you in advance for your recommendations!