Callebaut callets vs. block?
Low quality chocolate chips often have additives in them that help them keep shape and shelf life, that's why they're not recommended.  Callebaut callets are pure 100% chocolate according to Callebaut.  I'd use them anywhere for bar or chips with great results.  They might not come out of the oven looking exactly like a traditional chocolate chip cookie (for example) but they should taste fantastic!