This is a very rough (but hopefully not misleading) analysis of the Spaniard's power.
So, on T107, they had just surpassed our own power score of 138k. I don't have SilentConfusion's fancy grids, but it looks like they got up to somewhere between 145k - 160k total power. As we know, this is composed of pop, tech, buildings and units. We have visibility on all their cities now, so let's break down what we know.
Pop = 12k power for 25 pop on T107
Buildings = 12k power for 4 Ikhandas (I'm pretty sure the city we uncovered most recently had an Ikh in there, but maybe this is only 9k)
Tech = 28k minimum for Hunting 2k, Mining 2k, BW 8k, TW 4k, AH 2K, Maths 6k and Const 4k. Note that I have not included Archery since we haven't seen any archers in their land.
SUBTOTAL = 52K
That leaves us with about 90k - 110k in soldiers.
In Ulundi (cap) = 2k (garrison warrior)
In Umgung = ??? (maybe another 2k garrison warrior?)
Near Nobamba = 22k (2 cats + archer axe + chariot + warrior, this is their furthest city from us)
Near Bulwayo = 14k (2 chariots + warrior inside city, Impi guarding worker, these could threaten Ahbi)
Near KwaD = 29k (3 cats + impi inside city, impi and axe guarding workers, these could threaten Hansa)
UNIT SUBTOTAL = 69K
This leaves us with 20k - 40k unknown soldiers. Units they can build include warriors for 2k, chariots for 4k, impi for 4k, cats for 5k, and axes for 6k. If they have a couple axes and a couple impi in the fog somewhere, this would be at least 20k. If they have a few exploring warriors wandering about this could be another 6k. They can't have too many more cats around, since they just completed Construction on T102 and they've only whipped 3 times since then. And another chariot or two would make sense.
So, it seems to me that we may be looking at an addition 2-3 axes, 2-3 impi, 1-2 chariots that can threaten us, that we haven't already located.