12 long is a rad tank! If you can hang your light above the tank, you could adjust the height of your light to allow plants to grow out of the tank. Mounting to the wall, ceiling, or even attaching a bracket to the stand would work well. Lighting strength will also be dependent on if you plan to utilize pressurized co2. Co2 will allow you a more powerful light. 12 gallon long isnt very deep so you may not need anything crazy. A lot of folks like the Fluval 3.0 and its app looks to be pretty dreamy. There is also the new Auqaillumination Blade that looks pretty neat and I would say be on the brighter side for your tank. If you dont plan on injecting co2, you could use something like the Beamswork EA and would probably suit you well. A lot will depend on your goals and the addition of co2.
