ฟอรั่มสนับสนุนของ Firefox

I thought I had turned off autocompletion for logins, but when I log into websites, the username suggestion box still pops up. This is very annoying. See attached image for an example (edited to hide my actual username for that site). What do I need to change to get rid of this?

How are my bookmarks stored when synced between devices? Are my bookmarks encrypted as well as my passwords/credit card info? This is from the Mozilla page regarding encryption:

"Your encryption key remains a secret, only known to you and your authorized devices." and "We store your encrypted data on our servers so we can’t read it."

I just wanted to make sure this also applies to bookmarks before I import all of mine.

Thanks for any help!