If you don't mind using vue.js as your framework then you'll have everything already set, you can just open the editor and start adding your code. Spark has a nice feature that it will allow you out-of-box to consume the same API both through web interface (ajax) authenticated by cookies, and from another client authenticated by tokens. It takes care of all security and stuff and it all works very nice without any additional setup. Just add your api routes, templates and some vue components and Spark will take care of the rest.
If you don't want to use VueJS, then it's significantly more work to make the same functionality. If you need payments and settings (and you probably do) Spark will still save you a lot of time, but will also give you trouble when you try to integrate the Settings area (which is implemented in Vue) with the rest of your code. You will constantly find yourself work around & against it's presumptions.
Spark is well-written and modular, but still it's far from trivial to switch to the js framework, so it's better to stick to the VueJS, if possible.
