Even with a regular bike one of the fastest ways to learn balance is to lower the saddle till your feet can both reach the ground while seated and remove the pedals so that they do not interfere with your legs. Use your feet to push off and paddle along. Basically you are using the bike as a Dreisanne, the first bicycle design from about 1817 and the one that proved that we could learn to balance on two wheels.

Many kids have learned to balance a bicycle that way in an hour or two and unless you have medically related balance problems I bet that you can too. Then you can try multiple bike configurations and choose whatever you prefer.