Hello @candyhk20022002
Here are more details about Licensing.
https://download.microsoft.com/download/9/5/6/9568EFD0-403D-4AE4-95F0-7FACA2CCB2E4/Power%20Platform%20Licensing%20Guide%20November%202022.pdf
Power Apps are based on Three licenses Per user, Per App, or Pay as You go. You pick one based on the Usage of the app to reduce cost and they are required if App use any Premium future like Connector or Dataverse.
If it comes to the creation of apps, there are a few things You need to know.
1. Your Company will get something called Trial environment capacity which can be turned on by Your Admins. This allows You to build any type of app for a short time, around 30 to 90 Days, depending on whether you do an app for personal use or create a wholly different environment to create solutions and play with other futures. This allows for building Model-Driven apps and Portals with Premium connectors included.
Here is more about this:
https://learn.microsoft.com/en-us/power-platform/admin/trial-environments
2. As an E3, you can build simple Canvas Apps with SharePoint or Excel Online Data Sources. The Datavers and premium connectors will not be available, causing Portals and Model Driven Apps what require Datavers unavailable to You without the license.
After the Trial is finished, the Power App developer requires Power App per User License, and he will be able to create any app in any environment. This Means You will be able to develop their test and deploy them, and then it's about Your business to decide if the app is cutting costs and how to license the app or the users.
Here you have FAQ for License as well to speed up your learning.
https://learn.microsoft.com/en-us/power-platform/admin/powerapps-flow-licensing-faq
Hope this helps