TL; DR: I think you're going to do fine and you have a good plan.

You are correct, technically "Linux" is the name of the kernel. The kernel is to an operating system what an engine is to a video game, similar to how Subnautica runs on the Unity engine, Ubuntu and Arch run on the Linux kernel. There are a lot of options for the other components of an operating system, like the package manager, the init system, the GUI if any, the default apps, the shell, all manner of stuff like that, someone releasing their preferred combination of components is called a distro. There have been thousands of them, but I would suggest looking at Fedora with Gnome or KDE desktops, Linux Mint with the Cinnamon or MATE desktop, or Pop!_OS with their Gnome fork.

Installing Linux on one of your laptops is a fantastic idea. Let that machine be the experiment zone while you maintain other machines for your main workflows. For something like web browsing you'll be up and running pretty quick. If you've ever installed Windows before, you'll find the process of installing Linux familiar if not refreshing.

Gaming on Linux has come a long way thanks in no small part to Valve. There's one setting in Steam you'll have to check called Enable Stem Play For All Titles. Steam will automatically figure out if the game has a native Linux version and install that, or if there isn't it'll grab the Windows version and run it in Proton, Valve's Wine-based compatibility layer. Works very well. I would suggest going with AMD graphics if you're going to fully switch to Linux for your gaming setup, as their drivers are right in the kernel, no fuss no muss, and the newer Wayland windowing system (replacing the venerable old X11) works better on AMD or Intel graphics. Wayland is a little spotty on Nvidia still, so I might recommend something like Linux Mint Cinnamon that still uses X11 by default with Nvidia graphics. Nvidia does still handle compute and video rendering better, so if you're doing those workloads you may want to learn how to live with Nvidia.

Something I would suggest is learning to use the terminal. I know it's unfamiliar, but there are some powerful tools and fun toys in the terminal. Should you need to troubleshoot anything, you will probably hear "run this command in the terminal and copy-paste the output," and for two reasons: 1. it's easier to copy-paste terminal commands and their outputs in text-based forums like this one and 2. there's a bunch of different GUIs out there, with different methods of getting to the information you want, some might be more minimal and not have a GUI tool for it, but the terminal command always works. You can watch Star Wars in the terminal. Seriously.