Chrome on an M1 Pro Mac. This is the number that Chrome’s task manager shows me.

I do have a lot of emails, but I think it should only have to worry about 100 of them at a time, so I don’t know why it’s different for me and you. It is possible that my account still receives beta features, because I used to work there, but I remember it being like this for multiple years, since the new gmail came out.

Are you using Chrome through Rosetta? I'm still unable to replicate this on either my desktop or laptop, both of them just idle when I open Gmail and neither will push past 5% usage while I'm opening emails. Your metrics seem a bit odd here.

Same for macOS, Chrome. CPU sometimes jumps to 3%, but that's about it (and I guess that's because it uses slow core).

I have very clean mailbox, though.