9814 fixes addresses portals being spawned at (+16, +16) offset of the last fallen enemy. Depending on your relative position to the portal, this adds or subtracts a few frames from a run.
Changelog for 9826 was not entirely correct, since I did not yet test melee weapon behavior at the time (assuming that it's considered to not have ammo, while at reality it's considered to have 50% ammo). The way this works is, basically:
- Let drop rate multiplier be 0%.
- For each of weapons,
- If weapon is melee, add 50%.
- Otherwise,
- If weapon ammo is above 60% of maximum, add 15%.
- If weapon ammo is below 20% of maximum, add 80%;
- Otherwise, add 50%.
- If Rabbit Paw is obtained, add 40%.
Therefore, depending on your weaponry, your drop rate multiplier is from 30% to 160% (70% to 200% with RP).
In multiplayer, the multiplier is set to average of that between all players.
What the change does is that it clamps the minimum drop rate to (100% - health%) * 50%.
Therefore, if you have 1/8 health, but full ammo, your drop rate will be 43.75% instead of 30%. At 5/8 health it'll be 31.25% instead of 30%, and at higher health drop rate will remain unaffected entirely.
As can be suspected, this only situation where this kicks in is if you have >60% ammo in both weapons, since otherwise you have >50% drop rate multiplier as-is.
In multiplayer this has slightly more meaning, since players one hit away from death will generally stay behind, impacting the drop rate negatively if they did not also empty their weapons prior.
That said, yes, I can add a command to specifically toggle this one bit of behavior, but I don't think there's any meaning to attempt to group NTT with "vanilla" NT - many fixes inevitably have some sort of effect on balance.
For example, I've fixed the unreasonably consistent bug where the portal in 1-x areas would often spawn upon remains of one of the exploded barrels instead of the last enemy. Depending in situation, this would cost the player several seconds at the time.
Fixes to hitboxes for slug-like projectiles mean that targets can no longer be hit those 3 pixels of a slug projectile on it's last frame.
Cooperative elements are in no need of mentioning, since the original implementation was broken enough to be able to tease the game for lots of things.
There are also some balance-affecting changes carried over from u99 beta, such as ultra crossbow projectiles travelling slightly slower to make it impossible to fire bolts through walls and/or out of the level.
On topic of u99, even changes between official versions of the game most often have effect on balance, which is why daily and weekly leaderboards are separated by version.