I also like metroidvanias, and not really RPGs:
Cadence of Hyrule - I only played the demo, was really annoyed by it and did not enjoy it. (I'd say try the demo?)
Axiom Verge - One of my absolute favorite metroidvanias, great mechanics and level design. (Seen that many don't care for it though.)
Golf Story - Enjoyed it a lot, it has funny writing and the gameplay alright if you like golf-like challenges. A solid 3/5 where 3 means "good!"
Undertale - I've given it a chance twice. I just..... really don't care for story in my games, and I get bored and lose interest somewhere not far in. It's such a beloved game that I still think you should give it a try though.
What I'm saying is that it's subjective and you probably gotta find out for yourself.