Customise Pre-installed Android in personal Smartphones?

[raji...@gmail.com]

How is it possible for me to look into my smartphone's Android image and add-remove/customise the applications pre-installed with the customised distribution in my smartphone?

I also want to copy and save some applications' saved data, like Whatsapp chats, images and videos, in personal folders without having them backed-up in my Google Drive.

I don't wish to use the following:

Creating a Google Drive backup:

    Open WhatsApp.
    Go to Menu Button > Settings > Chats > Chat backup.
    Tap Back up to Google Drive and set up the backup frequency to your liking.
    You will be prompted to select a Google account that you will back up your chat history to.