The app is just NOT customizable enough. It's not possible to change the text on buttons and it makes things too difficult for a customer to checkout with a BOGO offer, for example. Especially if you're like me and you want to offer a free gift but your product has many variants then this app is likely not for you. Tried to to replace another BOGO app used in the past and just not getting the conversions I would like.
Tried to speak with support but they seemed unable to understand what I wanted to do. Possibly a language barrier, not sure.
You can edit any text via Settings > Translation. The offer does support multiple variant. Please check your inbox.