The way OWL described is that every three hours you get three skins. That means if you watch 6 hours you get 6 skins. Am I right? What other rewards are there? Are tokens doubled?
There are a total of 15 Overwatch League Gray and White skins that have not appeared this year. The first nine are earned watching on the Playoffs from September 21st - 24th, the last six are earned on the Grand Finals on September 25th. Full details can be found on pinned Streaming Rewards Guide: