You wouldn't happen to be running Tab Session Manager, would you? That was causing me all sorts of performance problems on both PCs and Macs, and I only tracked it down by disabling all extensions and themes and then incrementally re-enabling them.

I am not, although you did remind me to try without any extensions enabled again. I can't do a straight comparison as I'm at work now, but my work laptop (2017 vs 2016) is showing improvements. For reference, my work laptop also had high CPU usage on previous releases (even with no extensions), so there's hope yet. Although not being able to use the extensions I normally use would be a deal breaker (blockers and such)

For me it just consistently hovers around 18% cpu. Chrome on the same site sites around 1%... could it be optimized for memory usage isn’t always better if it means more cpu usage?

I'm at 2% right now typing this comment. Might be worth checking your add-ons.

I always run stock browsers. Usually in FF on OS X any kind of css animation is very cpu intensive.

Sounds like your computer. :)

I saw the same issues and I'm using a 2017 MBP 15" with the middle of the road CPU and 16GB RAM (dedicated GPU as well).