TYPO3 Core

First thanks for the reply.
The repace property will only prioritize the replacing with a plugin.
You are not allowed to replace the values with typoscript.

For example you can use the .field property to create a fallback.
This works:

twitter:title.field = twitter_title // seo_title // title

But with "twitter:image" and "og:image" this will not work.
You are not allowed to change the cType.

For example, this does not work:

twitter:image = IMAGE
twitter:image {
    file {
        import.data = levelmedia:-1, slide
        treatIdAsReference = 1
        import.listNum = 0
    }
}

twitter:image.stdWrap.cObject = IMAGE
twitter:image.stdWrap.cObject {
    file {
        import.data = levelmedia:-1, slide
        treatIdAsReference = 1
        import.listNum = 0
    }
}

I performed the following test on TYPO3 9.5.8

1) TS Setup:

page.meta.twitter:image.cObject = IMG_RESOURCE
page.meta.twitter:image.cObject {
  file {
    import.data = levelmedia:-1, slide
    treatIdAsReference = 1
    import.listNum = 0
  }
}

page.meta.og:image.cObject = IMG_RESOURCE
page.meta.og:image.cObject {
  file {
    import.data = levelmedia:-1, slide
    treatIdAsReference = 1
    import.listNum = 0
  }
}

2) Create at least three pages: "Home page", "Page 1" and "Page 2" (the latter two are subpages of "Home page".

3) Home page > edit page > tab Resources > add a file (fileadmin/test1.png)

4) Page 2 > edit page > tab Resources > add a file (fileadmin/test2.png)

5) Visit the three pages and look on the source code for the meta tags

Results:¶

Note¶

I tried to add to the TS Setup:

page.meta.twitter:image.replace = 1 
page.meta.og:image.replace = 1 

And the results are the same. Am I doing something wrong? Is this the expected result?

I'm sorry, to me this looks like the expected result. The typoscript provides the fallback so the image from the homepage is used on "Page 1" in your example.
Since Page 2 has an own image, this is the output.

Could you clarify what the needed result is?