For example, is there a version of linux that I'm missing? I've not run a desktop linux box in over a decade, any suggestions would be great, or is everyone happily running ubuntu / fedora?
I'm using ArchLinux with XMonad as my window manager. That's neat, though it doesn't make Firefox or VSCode any faster (nor slower).
I'd pump the brakes on Ubuntu, which nowadays is a perceptibly worse user experience than other mainstream distros. Snap is a disaster, and flatpak rocketed past it years ago thanks to Valve bucks.
PorteuX is also an interesting performance-optimised distro that takes a different approach - which is that of extreme minimalism (aggressive binary stripping, minimal packages) and its "Copy to RAM" feature (basically the OS runs 100% from RAM, so storage I/O bottlenecks are completely eliminated).
I've tested both on a 128GB Strix Halo laptop and haven't found much of a difference in terms of snappiness, but if you have older, more humble machine, I reckon PorteuX would definitely feel more snappy.
Finally in terms of snappiness, the DE you use also makes a huge difference. The PorteuX guys have just put together an interesting benchmark comparing various DEs and Wayland to X11 which is worth checking out: https://www.phoronix.com/news/Wayland-X11-Performance-Porteu...
My mum was on an Ubuntu base as well (Mint first, later Xubuntu) but after both eventually experienced failed dist-upgrades (no GUI after reboot), I switched her to an immutable distro (Aurora) and it's been rock solid so far. And in the event something does break, rollback is as simple as selecting the previous image from the boot menu.
So for normies who want a macOS like experience, I'd recommend Bluefin, and for Windows-like, I'd recommend Aurora. And Bazzite for gamers. All of these are Fedora-based immutable distros and have none of the stability issues that Ubuntu-based distros have, plus the generally newer kernel+mesa stack compared to Ubuntu means you'll also have better compatibility with newer hardware.