I remember back in the day, running Quake3 on linux provided better FPS than on windows. I haven’t compared the two since then on any game.

Is it still the case? And is this difference (mostly) there in other games too?

You have one per installed kernel. Not sure what (if any) automagic is common for removing old kernels, I guess this varies between distros, but at least on my computers, old kernel remain. At least the previous one, maybe more. It comes in handy in case a kernel upgrade breaks something, which it actually did recently on one of my laptops - makes it easier to boot from old kernel and revert.

EDIT: I just checked. I have just one on my daily driver. It’s quite new, and I don’t think I’ve had a kernel upgrade on that one, so it makes sense.

On my work laptop (the one with borked kernel upgrade) I have two.

So what you most likely have is one or more vmlinuz-version-numbers, and then simply a symlink named just vmlinuz to the version you boot from.

Short answer to your last paragraph:
vmlinuz is the kernel. It ends with z instead of x, because it’s z-compressed to save space. (I’ve heard that it’s possible to use an uncompressed kernel for that 1ms faster boot time)
Initramfs (not intramuscular, which my autocorrect thinks is appropriate) is a small filesystem blob, “initial ram filesystem”, meant to be loaded directly into ram to allow the kernel to talk to your hardware via drivers. It also has a lot of binaries needed to perform other tasks that need to run before the root filesystem is mounted.

Plural.

Can’t be arsed fixing that for you.

“It just works”

…because that is the state of a mainstream modern distro, and it’s not true of Windows anymore.

Alternatively “No nagging, no forced online account.”

cd /usr/ports/hammertothehead && make && make install

…for FreeBSD users

yum install melatonin

I would’ve liked to see him try mint instead. Less fluff, and hopefully that would’ve gone better for him.