Are sims cards interchangeable?

The sim card holds your phone number, and carrier settings. You can insert the sim card from your iPhone 6 in the iPhone 11.

To transfer your data, follow the steps in the following link. Its a fairly simple and straightforward process: link-> Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support

No. You can use either an iCloud backup or the quick start option to transfer your data without involving a computer.

Read the support document I linked to above and its included links.

The sim card doesn't contain any of your information.