Recruit/Convert after abduction?

[abyssalfury]

I have been using abduct to recruit/convert people. However, I don't understand what makes someone eligable for those two options.

I understand you can't use it against Rulers, this is people without titles. But sometimes I abduct someone and they have both options available; other times they only have one*, and sometimes neither. So how do you tell without having to abduct them first?

(*Not including times when you can't convert because they're already matching faith, of course).

[CrUsHeR]

In addition to https://ck3.paradoxwikis.com/Prisoner#Negotiate_release

I think you also cannot demand conversion from "devoted" (monk/nun/holy order member) characters