I am answering the File Upload portion of the question. I do not personally think a Text Editor and File Upload are related components, other than in the user interface you are building.
You can use an input type=text to edit. Are you wanting to display image data inside your textbox, like a Stackover flow post like this?

I am a little confused on your use case, but in my sample project Blazor Image Gallery, I upload profile pictures in my sign up component, but they are not display in a text editor, just in the component markup.
I have an open source project called and Nuget package called Blazor File Upload.
Source Code including Sample Project
https://github.com/DataJuggler/BlazorFileUpload
Nuget Package:
DataJuggler.Blazor.FileUpload
Another more advanced blog / sample project / tutorial / video
Building Blazor Image Gallery
https://datajugglerblazor.blogspot.com/2020/02/building-blazor-image-gallery-complete.html
Blazor Image Gallery Source Code
https://github.com/DataJuggler/BlazorImageGallery
Video: Building Blazor Image Gallery
https://youtu.be/3xKXJQ4qThQ
(Stackoverflow)
This is 100% directly answering the question asked, so please do not consider my free code that I give away as spam.