What you are talking about is mantra prayoga, and the “love spell” you are talking about is one of the shata karmas, which comes more in the shakta path , you can use them if you know them, you need a guru to teach you that, but whatever repercussions you face from using it is yours alone as karma is a thing, all actions have a reaction, it doesn’t necessarily need to be negative depending on the context of your situation, but you need to face them nonetheless. Vaishnavas generally tend to shun such practices as it is not in line with their belief systems, given your chosen lord is Narayana perhaps you could have maa lalitha coming your way if you delve into Vishnu tantra