If all of your pedals are 9V, why are you even looking at the Juicy Lucy? T-Rex makes a same-size power supply called the Fuel Tank Jr. which has only 9V outputs. You should get that instead.
Don’t risk using 12V on your pedals. Although some 9V pedals can run on 12V, most can’t. Most will be fried. It’s all a matter of components and design… some designers (more often, the boutique pedal makers) use components which can take higher voltages, but you’d need to ask them to be sure.
For example, the Fulltone Bassdrive can run on anything from 9VDC to 18VDC, and has more headroom towards 18VDC. However, it is designed and advertised this way. Don’t ever assume other pedals can take it, because they usually can’t.
