This sound pack (resource pack) replaces exp orb pickup sound with an empty sound and can be easily modified to replace level up sound the same way. It was tested on 1.20.1 but should work on pretty much every mc version and it does not require Optifine.
If you don't like the removal of exp orb pickup sound you can delete it or replace the sound else here:
"Disable XP sounds\assets\minecraft\sounds\random\orb.ogg"
You can also remove or replace the level up sound if you want by placing your .ogg file inside
"Disable XP sounds\assets\minecraft\sounds\random\"
and renaming it to levelup.ogg