The higher level falmer can easily beat a mammoth or a giant if you played to a very high level. Like what many people said earlier on, they are huge in numbers, since its being thousands of years after they became falmers. And since not many people wander into the falmer territory(or get killed), there are no potent predators of the falmer, so they will reproduce quickly.
The falmer armors and weapons are higher end and can easily match an orcish or even ebony. And since falmers according to the lore are good at range, they can easily beat any imperials. the chaurus is a bigass tank and can tear through a few humans. And i believe there are more falmers and chauruses in blackreach alone than there are humans(non fighting and fighting) in skyrim.
plus, have you seen the falmers' slaves? They are nords
