I'm trying to be clear about registry, and would hope someone might confirm, or not, that my interpretation is correct.

I read here

The parent of each 64-bit registry node is the Image-Specific Node or ISN. The registry redirector transparently directs an application's registry access to the appropriate ISN subnode. Redirection subnodes in the registry tree are created automatically by the WOW64 component using the name Wow6432Node. As a result, it is essential not to name any registry key you create Wow6432Node.

I think this means that when I read a registry key for example HKLM, that windows takes care of where to redirect my query to, if need be, and I do not have to worry about determining OSARCH in this scope.

Appreciate your reading, thanks.

You don't need to worry about that. Just call the registry functions and they will take care of all that complexity.