Does Avatar have a sticky cart option?

Yes, it does!
You can find this feature on the product page options

  1. Sign into your Shopify admin
  2. Go to 'Online Store' > 'Theme'
  3. Click Customize
    stickycart1
  4. Select Default Product section
  5. Click on Product Page option
  6. Scroll down and check the Enable Stick Cart options
  7. Save!

stickycart2