Now before I begin, I want everyone to know that I am a wizone.
A lot of people try and connect Hearts2Hearts with SNSD but in my honest opinion, they give me early IZ*ONE vibes, at least musically and conceptually.
IZ*ONE may have not pioneered the elegant concept, but when you think of elegance, they're the face of it. They embodied the hard hitting yet soft style of their title tracks and amazed the audience with their choreographies. However, they brought the cute pop sound in a lot of their b-sides and showcased their vocals in ballads.
In the same sense, I feel like Hearts2Hearts uses that same styling tactic. For The Chase, the teasers were a mix of bright and colorful while also showcasing a gritty darkness in others. The same feeling was used during IZ*ONE's COLOR*IZ teasers where some were a mix of cute girliness, and others a sharp elegance. Even the teaser video for the album showcased the girls in a quirky brightness while La Vie En Rose was a hard hitting, powerful song. The same could be said for The Chase where the debut trailer was really chill and upbeat, but then you get into the dark magicalness of the actual music video. And I feel that H2H continues this well with Focus where it blends a monotone darkness with a soft aesthetic.
Anyway, I'm not sure if I am making much sense, but the balance between chic sharpness and girly cute is what connects these two groups imo, and Hearts2Hearts is just a more modern and trendier product of what IZ*ONE was. At the end of the day, everyone can have their opinions of what they think, but this is just how I have interpreted H2H after their various releases.