To me focusing on several products prevents me from actually focusing and giving 100% in each, but I've interviewed some people who will say they prefer to work on several projects not to get bored and to always have something different to work on. But it is also complicated to handle mentally. Once your first product is launched and works well though, you can start working on the next one
Depends on how far you want to take your products. Do you just want to create a cool tool and show it to people? Then you can work on several. But if you want to take your project to the moon you have to be working on one at a time.
IMO you can truly focus on one product at a time. One can handle several side-projects or weekend hacks but they will be outside the full time work of that one main product (which most likely contains several projects in itself).