I always assume Errant is rated PG-13, it features:
Violence, including monsters getting limbs cut off (but crucially, they're always monsters who have glowy rainbow goo or dust inside rather than blood and guts), and some bleeding and injury (minimal).
Censored swearing, and minor swears like "hell" "damn" etc.
Alcohol use.
Sexually suggestive language and situations (though they come up more later).
I tend to use stuff like The Simpsons, Steven Universe or Enter the Spider-Verse as a guideline for what's okay to include.