Beacon & Conduit
Beacons' range now varies based off the blocks that made up the pyramid. Better blocks = more range. A full Iron pyramid gives about the same range as vanilla.
Also pets now get the beacon effects.
Conduits are also buffed increasing the range(by a lot) and the damage dealt to enemies.
Temporary Spawners
Spawners will be disabled after some mobs spawned. The farther from world spawn, the more mobs the spawner will be able to generate before deactivating.
When broken, spawners give bonus experience the farther from world spawn.
An echo shard (diamond in 1.16) can be used to reactivate spawners.
Explosion Overhaul
This feature enhances explosions by making them more deadly.
First off, explosions will damage entities even if they are behind blocks if the block is destroyed in the explosion.
Explosions generate in the middle of the entity instead of the bottom.
(1.16) Shields will no longer block the whole explosion, but only 50% of the damage.
Talking about knockback: the knockback scales with the explosion size, bigger explosion = bigger knockback. Bosses and non-living entities take vanilla knockback
With this feature you can enable back the poof particles on the explosion like pre-1.15.
There's also an experimental setting (disabled by default) that blasts away blocks instead of destroying them. Blocks that can't land will drop the block as a TNT would have destroyed it.
Tool Stats
Wooden and Stone tools are bad, durability is greatly reduced and MC 1.18+ efficiency too.
MC 1.18+
Iron tools have 50% more durability
Elytras have 1/3 of durability
Nerfs
Sheeps no longer drop wool when killed
Boats no longer go stupidly fast on ice
Iron drops from golems only when killed by players
Villager Nerfs
As soon as a Villager gets a profession, his trades will get locked and will not change by destroying/placing the Workstation
Villagers will also always convert to zombie villager regardless of difficulty and no longer get the bonus for begin converted back to villagers.
A trade can no longer get discounted to 1, max discount is now 50%
The demand will no longer go below a certain value to prevent an infinite amount of trades where the price will never increase
Debuffs on low stats
Getting low on hunger or health will now give you bad effects such as Slowness and Mining Fatigue.