I completed the System Architect Mission and got all the badges under the mission. Wondering if I get a certificate or something to prove my completion of this?
Nope, the badge you get is the proof of completion. You will be able to see all your badges in My Profile under Achievements.
Sorry just to clarify, in order to be a Certified Pega System Architect, I have to complete the System Architect Mission as well as the the Certified Pega System Architect exam is that right?
The Certified System Architect exam is sufficient to be certified as a CSA. After you complete the exam, you’ll get a certificate and badge/shield both. But it is always recommended to complete the mission before attempting the exam for your own practice.