The Copplestone Road Warrior figure is 25mm, soles of feet to top of head.
I use the Gaslands stuff for my 5 Parsecs games alongside Elheim "20mm," Hasslefree Grymm, Dark Future minis, some large 18mm stuff and a few small 25mm figures and some 3D prints rescaled for me to Gaslands scale.
The Grymm are a bit chunky but about the right height.
My older 20mm stuff looks a little small and weedy by comparison ... but some people are small and weedy, so I don't care.
Aliens range from 15mm to 28mm scale because how big are aliens?