Mary wants you to pray regularly. I don’t think she’s going to get too bothered if you are saying the Seven Sorrows chaplet rather than the Rosary, or if you decide to just pray the Liturgy of the Hours and not say any rosary or chaplet prayers.
Regarding the Divine Mercy, because it’s easier to pray than a rosary, there has been some concern among Church members that it is regarded as a “rosary lite” that might take the place of the more difficult rosary. I’m not really seeing that happen because many people I see at rosary groups either say both, or else they pray the rosary and leave when the DM is started. The DM is not a specifically Marian devotion, and has a different and specific purpose, so those seeking to pray Marian prayers will not see it as a rosary substitute.