A really important part of being an entrepreneur is knowing about different tools and how to use them. It's a great idea to the explore app builders and programming languages other than App Inventor! However, you should check out the submission guidelines for your division. You will notice that under the technical category there is a code checklist technical checklist that you need to complete with your submission. If you can't complete the code checklist or submit source code for a judge to view and test with the app builder you are using then you won't receive full points in the technical category.
If you have questions about what programming languages you can use, check out this article.