To start, I’d recommend checking out Flathub and seeing what’s available there. Flatpaks are relatively new but anything there can be installed on basically any Linux distro. It’s organized by category so you can see your options.

Chrome is available on Linux if you’re worried about switching. Firefox is usually the default and what I use just because I’ve always used it (plus, it fully supports ad blockers whereas Chrome now cripples them). Also, Chromium is essentially the exact same as Google Chrome. Both are made by Google and Chrome is just Chromium before Google adds all its branding and stuff.

Don’t worry about antivirus. ClamAV is there if you want to run a scan but you don’t need anything like Norton.

VPN: check your provider. Most work with OpenVPN or have a Linux client.

Gmail obviously works in the browser but there’s a ton of desktop email clients. To give three examples I’ve used:

• Geary is a simple, clean email client that just does email does it well. Not very customizable, though.
• Thunderbird (made by Mozilla) has more features/options and supports extensions. If Geary is too simple, Thunderbird is a good middle ground.
• Evolution is like the Microsoft Outlook that comes with the paid Microsoft Office Suite. It has a calendar and all that enterprise-focused stuff. Probably overkill but it’s there if you need it.

Windows 10 is listed and I’m not quite sure what you mean but you can always run it in a virtual machine if you need it. I use Gnome as my Desktop Environment. Gnome Boxes is super simple. VirtualBox is more complex but has every option I’ve ever needed.

Don’t worry too much about the Desktop Environment thing. KDE and Gnome are the biggest two and both are pretty much equally capable. (You can also always install stuff made for the other if you want. It just might not match the theme.) There’s loads of desktop environments but don’t be intimidated by all the choices. Some are stripped down and designed for older or low-spec computers. There’s one focused on Chinese users. You can ignore most while you get your feet wet.

On all microblogging platforms, I just follow people and periodically pare it back to something manageable. The sweet spot for me is following 200 or so people where a handful post all the time (and are fun and smart) but most are just friendly people, experts who don’t have poster’s madness (but add a lot when they do post). And some bots here and there for weather or breaking news but I’m very selective there. (I only want breaking news alerts that are actionable like, “A natural disaster happened.” and not 20 posts a day about political drama.)

That strategy has worked for me since the days of Twitter. It ensures there’s content for me to read when I’m playing with my phone but not so much that I’m unable to keep track of it all.