Overall, no surprises in your video. E-mail (webmail) performance plus Google eco-system/sphere performance ← varies. (Faster in the video, than WhatsApp.)
You have several Brave Browser Tabs (what you called “markers”), and every Tab is potentially a memory user and involved in background processing. Use the Brave Browser Task Manager and the MacOS Activity Monitor, in order to learn more ← Tip: Compare Process ID (PID) numbers.
Extensions (1 or more) that you installed, may be involved.
Also, your Mac computer model is unknown; MacOS version is unknown; Brave Browser version is unknown.
Brave Browser memory management, see Memory Saver setting at:
‘brave://settings/system’
May interest: