I’ve tried using Attack a few times over at least a decade, and currently have the iOS version on an ipad. Be warned that Attack’s quite buggy and Waldorf, much as I love their synths (I have a Pulse II and a MicroQ), aren’t the best company in the world when it comes to bug fixing. Or even making sure their products keep up with major updates to operating systems.
Heartbeat is definitely worth a look, yes it’s a bit “modular like” but it’s pretty good at what it does.