Go with the first option, since you have skills in C++. Flutter is well documented and a lot of hand-holding. If you find that you don't like that Wt backend af

Go with the first option, since you have skills in C++. Flutter is well documented and a lot of hand-holding. If you find that you don't like that Wt backend after some time, you can rewrite it with the second option. By then you are familiar with Flutter and probably will only have to do some minor modifications. GraphQL is good for when you want to arbitrarily query/populate data on separate screens for example, where you need a subset och merge with other data. Since it is a side-project and you write the backend yourself, you might not need that, because you can edit that code in REST on your own or just make a new endpoint. A big strong point for GraphQL is that it removes the communication and development friction between frontend and backend engineers.