Source Movement Warning
Moves you like Counter-Strike: Source, with bhopping and air strafing.
Your horizontal movement runs through Source's friction, ground acceleration and air acceleration instead of Minecraft's. Strafing in the air while turning your mouse the same way gains speed, and jumping the tick you land skips friction, so chaining jumps keeps that speed. Sneaking and using items slow you down the way ducking does in Source. It turns itself off while you fly, glide with an elytra or ride something.
Speeds and rates are in Source's own units, so the usual sv_ values carry straight over.
Auto bhop
Keep jumping the moment you land while you hold jump. With it off, every jump needs a fresh press, like Source without autobhop. On by default.
Max speed
Your top running speed, like sv_maxspeed. Defaults to 250.
Accelerate
How quickly you speed up on the ground, like sv_accelerate. Defaults to 5.
Air accelerate
How much speed air strafing can gain, like sv_airaccelerate. Defaults to 10, Source's default.
Surf and bhop servers often use 100 or more.
Friction
How quickly you slow down on the ground, like sv_friction. Defaults to 4.