For getting something close to i3 (you wont...?) on macOS I am using chunkwm https://github.com/koekeishiya/chunkwm.
I spent some time during the summer to get to know Linux using i3 (i3-gaps actually) with urxvt on a VirtualBox. I do recommend it!
And yes, scrolling with j/k for longer periods may be an anti-pattern in Vim and yada yada... I scroll in Vim, and in Alacritty its smooth, in Terminal.app its sluggish.
That said, there are plans to reduce Alacritty's input latency. Though, I personally use it as a daily driver and have never felt that there was a noticeable input lag.
Once that lands, Alacritty will have similar latency to Terminal.app _and also have_ a 60 Hz refresh rate (the "smooth" feeling), low CPU usage, and much higher throughput.