From what I gather, I don’t know that there’s a new norm in this regard yet, besides recognizing that gifs are increasingly old & clunky (despite being fun & amusing), and so I don’t know if mp4s or webms or something else might be better if wanting to keep a site lightweight while still having some animated elements.
Generally yes.
GIF’s ancient LZW compression is remarkably ill-suited for modern CPUs, and more expensive than modern algorithms. Combined with significantly larger file sizes, it costs much more to decode, on top of increased costs of transfer and caching.
GIF might have an edge if the animation is very small (<16px, few frames).
It also gets messy if you need to play hundreds of animations. GIF will be terribly inefficient, but also browsers aren’t designed to have hundreds of video elements, so both will eat memory in their own way, and it will vary which is worse.