So Linux is just the kernel. You still have to choose a distro and a Desktop Environment (aka DE) with an included Window Manager (aka WM) or a pure WM (like i3, awesome, QTile etc.) if you dare.

KDE is the DE you want that does all that Windows can do and much much more.

You can layout everything how you want it. Beautiful Widgets (e.g. for monitoring hardware, RSS, network activity) are built-in. You can put them on the desktop or into tray-bars (aka panels). You can have multiple panels, order them on any monitor edge you want or have them floating and show only when mouse-hovered. Multiple virtual desktops is a given since ages in most DEs (e.g. Mate, Gnome, Cinnamon).

It has a built-in facility to download new themes, widgets and scripts for kwin (KDEs WM). A lot of themes are gorgeous. Most of the scripts, themes and widgets are user-contributed.

If you own an android device, you're in for a treat as KDE comes with KDE-Connect. Best thing since sliced bread. Your phone will become part of KDE. Send files from the file-manager (Dolphin) and from the phone. Enter text on your phone from the PC-keyboard. Send the clipboard content. Use your phone as a remote via the acceleration and gyro-sensors. Show notifications from your phone within the desktop tray. Control music and video players on the desktop from your phone and vice-versa.

The file-manager (Dolphin) has Tabs and split panels to show two file-trees at the same time to easily copy files. It can easily integrate things like nextcloud or other remote filesystems like SFTP.

It's got KRunner which is a unified application-starter, calculator, search engine for your documents or the web and to quickly switch between open apps. It's a small textbox that shows up if you press alt-F2. It's fast and you can configure en detail what searches it should do (e.g. only your installed apps). If you dare you can remove all panels and the start menu from KDE via a few clicks and only use KRunner.

It's got a new built-in tiling manager (Bismuth is cool too) and much more.

So you need to decide which Linux Distribution (distro) you want. You mostly get them by downloading single-file iso's. Put those (even multiple) on a USB-Stick prepared with Ventoy. Start from the stick. Choose one distro from the start menu and boot into the live-system (which won't touch your hard-drives). You can start the installation on your hard-drive from a prominently placed button in the live-distro which usually starts Calamares (an easy as pie graphical installer). I can't stress enough what a good idea it is to buy a second SSD just for your linux system. Don't do win/linux dual-boot from one disk. Then within Calamares make sure you choose the correct SSD. Use systemd-boot instead of grub if there is an option. Choose not to many DEs while installing. Preferably only one. Applications are often programmed on specific DE-libraries (like gtk for gnome or Qt for KDE) but you don't need to install the full DE to use applications from another DE you haven't installed. The package-manager (you'll love it) takes care to install a small subset of those libraries automatically if you want to use an app from another DE.

The distro basically is an opiniated selection of packages, DEs/WMs and default settings for your desktop. Also they're mostly based on different base distros. Mint, MX, Ubuntu, Kubuntu, Pop! OS are based on Debian. Manjaro, Endeavour, Steam OS are based on Arch. Then there are base distros that don't seem to have spawned a lot derivatives like Fedora and OpenSUSE (both very good).

A big distinction between Debian based and Arch-based is, that the latter is a rolling release distro. That means that all your software, the OS, the DE gets constantly updated and you're always on the latest version. That means you can get some gigs of updates daily/weekly. So better don't be on a metered connection. If you aren't then rolling is a fantastic for gaming, e.g. OpenSUSE Tumbleweed, Arch or Endeavour. ~~With other non-rolling distros you often have to reinstall everything on a major distro-upgrade.~~ It had the misconception that non-rolling distros like Fedora or Mint have the need to be reinstalled on major version releases. But they have facilities like Ubuntu's do-release-upgrade.

Linux has another big plus: you won't have to ever surf to a website for bleeding edge software. The package-manager takes care and another big distinction of distros: from where comes the software (repositories), how was it build and how does the end-user install it. Arch based has something very special in its sleeve: The AUR (Arch User Repository) which is an addition to Arch's official repos and completely managed by users. If a package doesn't exist for Arch someone will prepare a script, that directly builds it from github (or other sources) and put that in the repos. In my 5 years on an Arch, I never had to reinstall the OS and there were a handful of times I need to download software via a browser. The other big advantage. The package-manager takes care of always keeping the apps up-to-date. You won't ever have to identify which apps need updates or where to download the installers. One click. Wait 1-5 mins. You're whole system is updated. No need to restart.

If you go with arch (on which the Steam-Decks OS is based), choose EndeavourOS. If you don't know something look into the Arch-Wiki which is often praised to be one of the best documentations out there. OpenSUSE has very big repos too and comes from a german Enterprise but they're very Open-Source, it doesn't cost a dime and is heavily praised in the community.

It all sounds very complicated and overwhelming. But it actually isn't. Buy SSD, USB-Stick, download OpenSUSE Tumbleweed, EndeavourOS and maybe Fedora or Mint. Boot. Install. Your Windows is recognized by the installer and will show up together with Linux in a boot menu upon restart.

This is my current KDE desktop:

https://imgur.com/a/AfnY7xn