As I understand it, the first would be 'devoted love interests', when the would-be-partners feel strongly for the mc.
The tag you mention would be if the MC wants to be with a strong person, since 'love interest' basically refers to the person the MC is romantically interested in.
For example. In DanMachi, the MC likes Ais Wallenstein, who is leagues stronger than him iirc. Or idolizes her, I'm not sure.
That would be a case of 'Strong love interest'...
Most Harem novels with a 'weak' mc (i'm using the term loosely) have a lot of strong ladies(or dudes) they are interested in, be it enslaving them, corrupting them, stealing them, or the more rare vanilla love. This then turns into a motivation for the protagonist to either grow in power, or use sleazy means to gain their favor.
Be warned that if you use the tag 'devoted love interests' the readers would expect no NTR, or wavering feelings from them, otherwise it would be a regular love interest, not defined by how strongly they feel about the mc.
Hope this helps!