Thank you, the methods depended on how I got the model in the first place.
For the N64 and earliest Mass Effect ones (up to Garrus) these were either ripped directly from playing an emulator or the game itself. So the poses are essentially what you saw on screen. As you might imagine, this gets tricky for Mass Effect because they're always hunches over in combat and after a while there's only so many fidget animations to deviate from a bland standing pose. Some poses have been rather roughly tweaked by selecting a bunch of vertices and manually rotating them, trying to keep proportions correct. Eyeballin' it in honesty.
Both Midna models were T-Posed or in a unsuitable pose from a Super Smash Bros. trophy. By now I learned how to rig things in Blender (actually, *squeezycheesecake did it for the Twili version, which is how I figured it out eventually) so things were moved more accurately with bones/armatures.
But the ME3 models were obtained from the game files using the Umodel and 3DS Max combo, which gives the massive bonus of being able to import animations too. So for those I can trawl through the game to find some decent pre-packed poses as it were. If I need to make adjustments, this ripping method also preserves the rig which can be really easily adjusted in 3DS Max. I suck at every other aspect of that program (overly complex- I can't even figure out how to apply textures) so I still export over to Blender to do the main editing.