One of the biggest things that BOOM! Studios' comics have contributed to the Buffy the Vampire Slayer franchise is the Slayerverse. The Slayerverse is the in-universe term coined during the 2019-2022 run of the Buffy the Vampire Slayer comics. The Slayerverse encompasses Buffy's version of the multiverse, each world spinning off from the original Buffy TV show in varying ways.
The conception of the Slayerverse has helped give the franchise a newfound longevity that has allowed BOOM! Studios to cover completely new stories from entirely new realities without contradicting the main canon continuity (which itself continued and concluded in a series of comic-only 'seasons.') Stories that include Willow becoming the Slayer, Buffy as an elderly woman during the apocalypse and even the show's theorized universe without shrimp. Each of these stories within Buffy's Slayerverse adds a new layer to the original series that allows readers to think about the lore in new ways and to explore the characters from a modern, updated perspective.
For instance, in Buffy the Vampire Slayer #31 by Jeremy Lambert and Marianna Ignazzi, Buffy and her friends hop from universe to universe recruiting different versions of herself to take on the Multiverse Man, Silas. Out of all her variants, one of the standouts is from Universe 12, a literally buff version of Buffy claiming to be powerful enough to lift a U-Haul truck. This puts into new perspective not only a Slayer's strength but its potential.
Slayers Can Enhance Their Powers
It has been long-established that all Slayers like Buffy have natural superstrength as a power. While Buffy and other Slayers have showcased exceptional feats of strength in the past, it has never been mentioned whether a Slayer can still get stronger or if their superstrength is naturally at its peak. It's been established that Slayers are physically stronger than most vampires, but especially considering that Buffy has faced foes stronger than her, it begs the question if a Slayer can enhance their own strength, ideally through training and skill.
Buff Buffy seems to answer that question, as her overwhelming strength surprises even the series' central Buffy. This version of the iconic Slayer seems to have actually put in the work to bulk up her physical strength on top of this Buffy's Slayer strength. Audiences certainly haven't seen the original Buffy or any Slayer lift the equivalent of a U-Haul truck before. While enemies like cyborgs, for example, have proven to be stronger than Buffy in the past, this Buffy seems to be strong enough that she could lift a heap of her rivals all at once. Earth 12 isn't just the strongest Slayer audiences have seen in the Buffy the Vampire Slayer franchise, but points to the idea that by increasing their muscle mass through training, Slayers can upgrade their superstrength in a major way.