PSR gives average figure heights in its Red Box Alliance figure pages. I intermix 25's with 28's because for the races I need, and for the figures I can afford, I accept the size discrepancies. On the tabletop, I can ignore the size differences for the most part.
For true 25's, yes, the Red Box Alliance figures are compatible, for the most part. I use their Warg Riders as Goblins, even though their "Wargs" are on the small side. All of my Wolves are from Prince August Fantasy Molds (Goblin Wolf Rider), and I put Caesar plastic 1/72 Goblins riding my lead-cast PA Wolves. I feature them side by side, without issue, for me.
I am more into gaming, than I am figure accuracy. This is because I tried, for several years, to collect figures in proper proportions to one another, using the 1978 1e AD&D Monster Manual size listings. What I learned, painfully, is that sculptors and figure makers never followed anyone else's sizing -- they made up their own minds as to what size fantasy creatures should be.
I began shopping carefully, looking at figure heights, to get the races I wanted, in as close as possible, sizes/heights as I could. I did the ratio math to figure out what sizes the creatures should be, relative to a 6-foot Human @ 25mm. I found, for example, that 1e AD&D Hill Giants should be 54mm (toy 54mm Cave Men figures are perfect!); and, for Frost Giants, a 60mm tall Viking Figure is also perfectly scaled! After that, things became much more difficult.
Gnomes are supposed to be roughly 3-feet tall, but most of the Gnome figures made, are around 4 scale feet tall, same as most Dwarf figures. I bought a bunch of Essex Gnomes, and I am happy with those: they were as close as I was able to find, affordable, and discernibly different in sculpting style from most Dwarves; a different paint color scheme further differentiates them from my Hill (3.5 scale feet tall: Caesar plastic 1/72 Dwarves) and Mountain Dwarf (4 scale feet tall: em4 plastic Dwarves) armies.
I walked away from the Scale Wars, buying what styles I like, in what sizes I am willing to accept on my tabletop. I game a lot easier now.
If you truly want figures of the correct style, and the correct size/height, I suggest you dive into 3D printing. This is the only way you will be able to control the proportions and heights of your own figures. It is an entire hobby unto itself, and I choose to pass on it. Cheers!