Transform and Marketplace - How do they relate, and who controls the available tools?

Hi,

I am trying to learn more about AWS Transform and AWS Marketplace and how they relate to each other. Are the tools/services available in AWS transform sourced from AWS Marketplace, or are they a completely seperate catalog?

If they are connected, who decides which tools are used within AWS transform - is that configured by AWS, or does the user have control over selecting their own connectors and services?

Also curious how tool selection works when there are many similiar options available. For example, if multiple companies have RAG based tools or agents connected to Transform, how does the system decide which one to use for a given task? Part of this seems to be based on the modernization focus selected (e.g. Mainframe, Migration, Windows), meaning each focus area only has access to a specific subset of tools? Though beyond that, I'd be curious how this is decided.

I know I jammed multiple questions into this post, thank you for taking the time to read and respond!