Whether you'll be doing the exam online or onsite, no books, notes, smartphones, smart watches are allowed: it's you and the screen (and the people behind the webcam or the exam room who are checking that you are not cheating).

I've never attended an exam at a proctored site for the following reasons:

• None of the cities on the beautiful island where I live have a certified exam site.
• To do the online proctored exam, you just need a laptop, a webcam, a reliable internet connection, and a quiet place.

If you plan an online exam, remember the following:

• Don't wear watches.
• Put your smartphone in silent or plane mode.
• Don't use multiple screens.
• Don't drink/eat during the exam.
• Don't wear sunglasses, and if you (like me) have to wear normal glasses, they'll ask you to show the glasses to the webcam (to prove they are not smart glasses).
• Don't talk or read the questions out loud or point out to the screen with your fingers (I did once and was asked to stop).

Have a read at the following Trailhead article to get more info about both types of exams at https://trailhead.salesforce.com/help?article=Scheduling-an-Exam.