We know vamps are stronger than humans, at least on average.... though I don't think all of them are peak human based on performance against Scoobies....but maybe peak for their body size and musculature....And older more elite vampires in the Cap to 1 ton range
We also know Buffy could easily lift the troll hammer one handed and Spike couldn't lift it without maximum effort. She could bend the bars on jail cells as well. Her strength wasn't played up a lot, likely do to budget constraints, but I'd put her in the Beast ballpark.
Dude, she's struggled to break metal chains on more than one occasion. Chains. And one time a metal chandelier fell on her and it took an entire episode just to get it off of her. She is no where near Beast's strength level. He can lift at least 10 tons and Buffy is no where near that.
It's interesting that a hero/villain performs one amazing feat, or use a power they haven't used for 20+ years, and that automatically propels them to a high status despite scans and evidence to the contrary. I don't know what is worse, selective feat picking that has only been done once or twice 20, or more, years ago or ignoring evidence from scans or the lack thereof. We need to stop putting our favorite heroes/villains on pedestals and start putting them where they really belong. But it's evident that people never will because they would rather accuse others of cherry picking feats, when they don't, and being 'morally superior' when they aren't. I guess being honest and as fair as possible only opens one up to being the target of childish accusations and fault finding by those who insist on acting petty and childish. What happened to a good debate between two civil, mature, adults?