The two things that lead to bloated save files:
1) Nirnroot glowstacking
2) Enemy weapons and arrows (including bound) not cleaning up properly
Quoted for emphasis.
These two are my biggest issues as I wish to play a character other than Janitor class.
Note the wording in this patch note, though:
- Arrows and other projectiles that were stuck in objects in the world now clean up properlySo, as it reads, arrows that lie about after striking walls or rocks will not clean up properly?
They're not stuck in anything. Your character can move them by walking over them.
Clarification from Beth (not conjecture or guesswork from the forum) is needed before we see that patch note as a clear positive.