It basically means instead of relying on a bootloader (e.g. GRUB or systemd-boot) the computer boots the kernel directly. Generally there should be no change besides having to use the BIOS menu to manually select a kernel.
For near-guaranteed compatibility, there are dedicated manufacturers like System76 and Tuxedo. Framework also claims Linux compatibility but for set tested distros (Ubuntu and Fedora).
Generally, anything with Intel/AMD graphics and Intel Wifi is pretty much guaranteed to work in my experience. For laptops, high-DPI displays can be problematic but the fixes are on Wayland which is getting higher priority now.
Not just that, soon after the US election, the UK will be gearing up for their General Election. Latest is the end of January 2025 according to a quick search.
There are Gentoo distros that have binary packages, and Funtoo (a Gentoo-based distro that’s 64-bit only) even suggests using Flatpak for certain software that needs 32-bit resources like Steam. Hell, you can install Flatpak on Gentoo if you want. Gentoo also provided binary packages in the past but only for a few packages (mainly web browsers, but annoyingly not qtwebengine. maybe that’s changed here.)
Gentoo is more about having fine-grained control of your system than anything else nowadays. If that’s what you want, go ahead! For most people, Arch or even something with less control like Ubuntu or Fedora will suffice.