My growing collection of rpis includes an rpi2 with a usb wifi dongle that still gets a fair amount of use. Mostly for experiments, but truth be told, it's not an old slouch.
These pi models are all tailor-made options. I think its a mistake to think in terms of "older models" when you consider the lower power requirement and higher physical stability of the rpi2 (doesn't overheat even without a fan, for example). The Zeros are less powerful but still belong in the range because of exactly that.
One downside to the 4 is that it is moving from the low power to laptop realm in terms of power consumption which was my main interest in them. If top performance is what you care about, the Raspberry Pi is the wrong place to go looking for it.