Yes. As a member of the Stygians community, I can confirm that Sacchim, Zoomutt, and any other artist you might pick out of the bunch are completely different people. Much of the art you chose to speculate on is older, and one of your examples is from a different artist entirely. The artist
behind this piece is
porkbun, and the reason it was posted to Zoomutt's account in the first place is because Zoo runs the Stygians ARPG from there. Her account can look confusing from a glance because of this, but she always gives credit to the artist in the description of the post.
I would also like to point out that the Pokémon art you posted is quite literally from 2005. 16 years ago, when everyone on deviantART was doing the exact same thing and drawing in a similar style. Zoo was barely a teen at the time this was posted, and she talks about this period in her life relatively often in the ARPG server. The artwork you chose for Sacchim is also
from 2015, and their recent art is
far different than anything Zoomutt has posted. The concepts are similar mostly as a matter of coincidence and, I hate to throw around this word so casually, but cherry-picking as well. I struggled to find the artwork you chose for your comparison (barring the pixels), but
here (and
here) they are in full. The first one (the spider) was from a free raffle, and Zoomutt usually sticks to a handful of aesthetics and palettes that she knows will appeal to the majority of the community, rather than something more specific.
These are her
three most recent pieces of artwork, credited to three different members of the Stygians ARPG staff because they drafted the original concepts, and Zoo later finalized them for the auction.
Here are
some others, to cover a broader scope of designs and color palettes. For comparison,
here are
some Sacchim works from 2018 onwards. I hope the difference in style is more obvious with these examples laid out for comparison.
Also yes. Unfortunately, these bids are entirely serious, and all from different people — the highest bid is now $1200. The only thing that breaks from the usual auction flow is the massive leaps that Sacchim and Citrusssss took, starting the bidding at $500 and skyrocketing to $1000. A lot of the $100-500 and $500-$900 crowd (you can see them show up in other auctions, and they usually bid in $10-25 increments as is standard) were completely circumvented by this, hence the appearance of artificial inflation. Waschmittelpulver (as much as this thread loves to dunk on her, and for good reason) is an insanely popular artist in the community, and her designs are coveted by normal players and auction whales alike. And the worse thing?

This is par for the course for a Wasch auction. The last one hit $2000, and recently, someone popped into the Discord server to incessantly spam the ad channel looking for a Wasch design and offering upwards of $3000. Otherwise, the current auction trend is actually starting to drop, and most auctions are barely hitting $1000 this time around; we moved out of "normal" sales into "premium" sales territory late last month (as the current event nears its end), and typically, "premium" sales net around $1500 each. People are sincerely willing to drop $2000 on this shit.