I second the recommendation of Linux Mint. Try a Live USB, and see if it feels fast. If it does, it is a great option.

In terms of theme, have you considered that Linux Mint’s theme is sexy as hell? I wouldn’t install it apologetically. I think it sells itself well.

Edit: and the practical stuff is all in the same places as on Windows, anyway. Start menu is in the lower left. Bar is along the bottom. Time and network applet are in the lower right.

The few ways I have noticed it is different seem to be because Mint doesn’t require corporate branding and names a few things in plain language, instead of MS jargon.

To me, XMPP is still the instant messaging gold standard. Everything has an app (or seventeen apps) supporting it, and it tends to just work.

My experiences with XMPP are: very good.

Matrix does more. I have used it on and off for fancier online meet-up type stuff. As others have said, it is relatively new, and that has various costs and drawbacks.