1.18.2 client-side mods that are handy and improve the experience for SMP & best for [FPS boost]

Fps boost mods:

Sodium - better rendering engine for huge fps boost
Phosphor - improve lighting engine
Very Many Players - improve performance at high player count
Better Fps - Render Distance - make render shape from square to circle, saves chucks that don't need to be rendered
Cull Leaves - cull leaves for better performance boost
FPS Reducer - reduces unnecessary GPU and CPU load by reducing fps when you are AFK
Better Biome Blend - improve biome blend and makes it no longer impacts performance
Distant Horizons - let you see farther with the same render distance by rendering fewer details
Entity Culling - skip rendering entities that are not visible
Dynamic FPS - reduce the speed of render when it is not focus
Spark - improve lighting engine
Alternate Current - improve redstone lag issue
Better Beds - improve bed renderer
FastChest - improve the dynamic chest model to get better performance
Ksyxis - speed up world loading by not loading nearby chunks every time

Not fps boost mod but help your game run smoother:

Lithium - improve server tick time
FerriteCore - reduce memory usage
lazy-language-loader - change language faster by not loading texture
LazyDFU - loading faster at opening loading screen by not loading unnecessary data
Smooth Boot - take less CPU usage when opening loading screen

Better vanilla improvement mods:

There are some mods that may not allow in some servers like:

Auto Fish - fish automatically for you
AutoSwitch - switch tools that break blocks faster for you automatically
Freecam - make you like spectator mode without op
Replay mod - record any world like making a copy of it
Full Brightness Toggle - allow you to have full brightness by changing gamma

Make sure to get the permission from server admin/owner before using it! :)

BEST Fabric client-side mods [FPS Boost]