Voles are tiny, like field mouse sized, and they're also short and fat. Stoats are long and thin, like a ferret. They're also much larger than voles. If whatever you have is one or the other, it'll be hard to mix up between those two if you can get a good look at it.

They can nest in pretty much any nook they can fit into, especially if it came with a tasty mouse snack. Doubt they would spend much time in your house though as they tend to roam their territory rather than stick around to a particular spot.

According to a search I did last night, while that's not impossible, it probably isn't a marten as they tend to have dark coats. The animal I saw had a pure white coat. In fact, I think it came through my crawlspace, which isn't clean at all; part of why it startled me is because its coat was so clean and bright coming out of a likely at least dusty space.

From the same search, I suspect the rodent might have been a black tailed ermine. I didn't see the tail, though, so I can't confirm that part.

Thank you guys for your suggestions!