CAG's Twitter and Facebook already posted the 20% announcement, but I guess the company chose not to advertise the second part.
Unless plans have changed since yesterday, for orders during the event, any order over $29 is going to give you a bonus $5 rewards. I'd recommend splitting your purchases up to take maximum advantage of this. $29 is also the threshold for free shipping so you won't lose out there. Reward points take 15 days to generate normally, though I don't know if this will be giving you enough points for a reward or directly giving 5 dollar certificates.
Obviously intended to compete with Amazon's Prime day, it starts at 6 PM EST tonight, 7/10, and runs for 36 hours until 6 AM on 7/12. There aren't any major sales for it to stack with unfortunately.
Most video games, accessories, and gaming related merch should qualify but:
Excludes Switch games