To be honest, I've never heard of Bash's @Q solution before today--I can't find it in https://tldp.org/LDP/abs/html/, which is my usual goto guide for "how do I do $ADVANCED_FEATURE in bash?"
In particular, failure to mention `printf -v` is horrible. Not only is it better performing than creating a whole process for command substitution, it also avoids the nasty newline problem.