2.) Appears like elves (Most likely Humans too) still think they are Dwarfs when it comes to gear size.

When setting a stockpile Un-usable gear sized for humans/elves will show up which shouldn't happen since Humans and Elves are larger and need those Medium/large clothing items.

Also happens in the reverse, goblin/dwarf clothing from raids will show up in Use-able weapon/armor stockpiles even though the Humans/Elves can't use them.

(Fix, if possible change the way stockpiles sort use-able items based on the CIV)

Elves dwarves and goblins are actually the same cubic size in vanilla of 60,000cm3, just that dwarves have modifiers that after the fact that make them slightly shorter but not in a significant way that they can't fit in each other's clothes.

Humans outright are 70,000mc3, the only midway you could find they fit in both is with clothes made fitted for hyena-men. Usability is about whether they are damaged or not, not that they're suitable for the fortress inhabitants.

From what I could tell, each race has a flag telling the game what "type/size" of armor they are allowed to use. So something "made for dwarfs" won't fit a human/elf but can fit like a goblin. In the base game I believe most factions make armor that is sized to the Dwarfs. But will wear the larger/smaller gear themselves.

The error happens when you're playing say Humans or Elves, and get a stock pile of Goblin gear. The goblin gear like you're saying the game "thinks" the elves can wear it but when they try to put it on the "small size" flag will tell them it's a mismatch and they drop it. The same thing will happen with "larger/giant" armor and clothing from were-people.