it seems to be a hole not letting ADMIN check the permission of a user.
Yes, I agree. I can’t see any reason why admins shouldn’t be allowed to check permissions of other users, especially that it’s already available in the UI.
can I use expressions as part of conditions as part of context parameters
It should be possible. When it comes to syntax, it should be the following in this case (the expression itself is not in any quotes, like other arguments in other inline conditions):
&classicProject={condition.jira_expression(expression=project.style=='classic')}
Let me know if that doesn’t work, I’ll investigate further.