PBI version control with Azure Devops - should I keep the pbix or the pbip to develop ?

I have a question regarding the DEV part when working with PBI and implementing the version control with Azure Devops.

The DEV is done on a pbix file to develop :

• a report
• a semantic model

There is something not clear for me, if I work on a branch and I push my work, I saw that before that I need to save my work from pbix to pbip.

So logically I need to push also the pbip into the branch I am working on to use it later if needed for example to add something or modify something like below :

so in future developments, I will only work on pbip for something already existing.

and if I have to add something new I work on pbix then save it as pbip and later I keep tracking only the pbip and using it.(and not the pbix anymore?)

Is what I understood or the way I am doing the version control is correct ?

When to use the pbix and when to use the pbip ?