Even the keyboard design itself can effect typing results. Like typing on a really good mechanical keyboard is more comfortable than a shitty chiclet keyboard.

there are two big arguments for a denser layout, notably you move your hands less, which means you can type faster, statistically speaking. It makes it easier. Generally you see typing speed track roughly with this over time.

And since you move your hands less, it's ergonomically better for typing, so you get less strain, you have better ergonomics in general, you can type longer, and even faster since there is less strain.

Different layouts optimize for different things, some optimize for efficient roll combinations, some optimize for switching between hands as optimally as possible. Some don't really do any of that (qwerty) which also have a significant impact on typing.

Layout isn't really about speed, it's about comfort
I've been using modified colemak for like a year now and good lord it's so much nicer to use: you just place your fingers on "arst neio" in my case and then 80% of the keys you actually use on a regular basis are within a tiny finger movement to reach.
And then there's the fact that you're almost always using a different finger for the next letter, suuuper smooth typing experience.

I originally learned qwerty and touch typed at 60WPM, during a really boring job before smartphones and before we had internet to the desktop at work and I entertained myself learning to type again, but on dvorak

So after 3 months I was back to 60WPM

I really like that dvorak has all the vowels on the left of the home row, and t and h are on the right of the home row right where finger tapping cadence works for "th"

So my speed hasn't increased, but my fingers don't need to move as much for common words. I don't think it's worth it if you play games on the computer, many games don't map keyboard controls well. Eg Minecraft moves everything to whatever key is in the same place as the qwerty key; 7 days to die doesn't change anything, so you need to choose keys for everything, or if you're happy with the defaults, just change the ones that conflict when you fix "wasd" to ",aoe"