Re 1: You are right. For now. stable is in a transition state. As soon as F41 is ready, it will be promoted to stable.
:stableand:stable-dailywill upgrade to F41 a few weeks later.
Source: Bluefin and Aurora F41 builds now available
Re 2: “ungated” has been introduced with fix: switch latest images to use ungated upstream kernel by p5 · Pull Request #1722 · ublue-os/bluefin · GitHub
It means, that the latest kernel provided by upstream will be used. When it is “gated”, then it uses the kernel from CoreOS stable. The term is also defined at Administrator's Guide (section “Gated Kernel”)