Linux

PopOS deals with nvidia drivers splendidly, if you'd Mike to stay in gnome

Linux Mint has a firewall built in so you can stop apps from connecting to the internet.

If you're coming back from Windows I would recommend Linux Mint Cinnamon edition. Easiest transition.

KDE doesn't suck anymore with regards to being overly complex/customizeable, not for the past two years. It's still powerful but a lot of those crazy options are hidden away. It's also quite resource efficient.

I personally really like Mate and would recommend it. As for simple wall, these are the stuff AltenrativeTo lists.

https://distrotest.net/index.php#U this website provide VM for testing you can have a quick look all DEs in very less time.

I keep going to back to XFCE and Mate. Mate being the most simple. Modern is very subjective. I would say neither is modern, but Modern depending on how you define it can be a blessing or a curse. I run KDE on one computer just to keep me up to date. Its cool but complex. Gnome - I wont touch, it obfuscates the operating system with its modern simplicity.

As for distros I am big fan of Arch and Manjaro. Arch for when you have time and Manjaro for when you don't. The rolling release makes using computers fun again.

gnome no longer defaults to wayland, which means performance on nvidia is normally just fine. I'm not a gnome fan, but it's won me over the last few years. kde has come on a lot too, but it's still a little hectic compared to gnome. you pay ease of use for customization. gnome has opinions, kde has options. if you want a gtk desktop that just works, budgie is nice. xfce and mate are awesome, but they're very old school, fine if you want to put in the effort, but for out of the box use, I'd suggest cinnamon or budgie.

cinnamon is very simple DE

XFCE for performance Mate or Cinnamon for the windows-like experience Gnome is probably the most resource intensive. In any case, depending on how long ago you had issues, it may be the case they have been fixed (unless Wayland is your thing, I think)

#1 Budgie is rather lovely - has some polish. But..

When you say you are looking for simple, modern and customizable it opens up a whole heap of questions.

Simple to me is a tiling workflow. Overlapping windows as a rule don't make much sense to me - very clunky way of going about things.

Modern - what is modern to you?

Customizable - which parts of the thing are you looking to customize?

Try out manjaro cinnamon or xfce edition. Personally I've been using garuda linux dragonized edition kde. On firewalls, I've been using gufw, which is not complicated

I'd give Solus (Budgie) a try. It's really well put together. I've tried nearly all DEs and I think it's the best to return to Linux.

Elementary OS is really nice, and has SO much potential. But the current release is based off of Ubuntu 18.04 and is a bit behind on SOME software, especially development libs.

1. If you want "it just werks" then you should use either gnome or kde. If you some snappy hacker-ish DE, then use i3wm or other window management program of your choosing.
2. That's just the default UFW lol

I can't comment on #2, but in so far as #1 goes I would say that if your looking for something 'modern', Xfce would be a waste of time. I love Xfce, I was a long time user, it does some things I like really well, for instance Thunar can be programmed with terminal commands for it's right click menu from within it's preferences, which is something I miss to this day. However 'modern' is not a word I would use to describe it... Xfce is effectively just the best of the desktop experience from a decade or two ago (which is not bad were that what you wanted).

I wanted something modern too, which eventually landed me on KDE. In terms of modern features for me nothing else approaches KDE Connect (even though I can't reliably transfer files with it without them becoming corrupt), though you can use that in other DEs I'm told. KDE's complexity is from is customizability (which is a bit too much). I would argue that if you can get it set up the way you want it, most of that complexity can be safely ignored.

1. I would also recommend Cinnamon. It's simpler than KDE and more modern than Xfce. Not as customizable as those two, but unless you're looking for extreme customizability (and would be fine with the added complexity that comes along with it), it really should be fine.
   Cinnamon is sort of developed for/by the distro Linux Mint, which certainly would be a fine distro to start out on, too.

2. This is a somewhat shitty answer, but it's a popular strategy among Linux users to just not install programs which you do not trust.
   I'm saying that because, well, maybe that is a valid strategy for you, too.
   But I'm also saying that, because that is why Linux is generally less well equipped in the fight against your own system than other operating systems may be.

2. https://youtu.be/JINRru-W1_s I'm not sure this will fullfil your needs, try once.

#2 opensnitch

my only addition is if you happen to have a hidpi screen, check out if your choice does well with fractional scaling. My experience a couple years ago was that Mate for example didn’t do so well but that may have changed.

I'm not sure which version of Gnome you used before, but Cinnamon is a fork of Gnome 2 and pretty popular. Looks fairly similar to Windows out of the box. Xfce is another popular choice.