the dlc is incredible!! there are jumpscares, and if i'm correct reduced frights reduces some elements of the scare itself without fully eliminating the jumpscare. additionally, reduced frights changes a specific game mechanic that can allow you to complete the dlc without ever getting jumpscared if you're good. personally, I found that reduced frights felt more like the base game, and Echoes of the Eye relies far more on scary vibes and ambience than jumpscares, so you're not missing much if you use reduced frights.
even if you're not one for horror games i very much recommend playing the dlc. it's got hours worth of gameplay, some really out-of-the-box puzzles (even in comparison to the base game), and ties in to the overall storyline at the end β really i consider it to be an indispensable part of the game. just like the base game, i'm really jealous of anyone that has yet to play it.