The Can't keep up Message is also common and always pops up while discovering new areas or similar - chunk loading always causes some lags - this message just says the server is lagging
For the other 2 - I have no idea
Most errors are from betterx - maybe contact the creator
Looks like this mod is looking for a fabric.mod.json in each mod - but not every mod contains this file
The rest are recipe/advancement errors - these are common and can be ignored - mods making changes at recipes/advancements