If you don't mind I'm going to go a bit 'architect' on you :-) Do you need a software architect or do you need a senior engineer. Interview questions are about finding out if you should say 'no', by definition if someone is called in for an interview you've tentatively said yes to them for the job you just want to know if you should change that to a no. So the problem set is understanding if the applicant in front of you will be able to do the job you need done.
Your comment that "in our org ... they are also hands-on" is the an echo of the Joel Spolsky 'architecture astronaut' type. Someone who spends all day architecting and none of their time coding. But here is the thing, at the end of the day its about how much product the organization ships at the end of the day and whether or not that product had does the job it needs to do right? So there is some nuance there to consider.
I certainly believe that anyone who considers themselves to have software architecture skills, should also be able to do anything a senior engineer can do caveat a deep discipline/subject matter engineer[1]. So interviewing for senior engineers will also get candidates who show architecture tendencies, and you will recognize them because of the questions they ask. If you want to provoke those questions then leave some of your coding or puzzle questions a bit ambiguous to see if they let their ideas play out or if they are sticking with the task.
Here is the thing though, you can have lots of really good programmers and all they need is a bit of structure around where they are going so that together they can make something awesome. That needs an architect who is spending all of their time keeping everyone on the same page, and if changes need to be made, moving to the new page. If your programming team is fairly senior and just "gets it" and will work out amongst themselves which parts need to fit with the other parts, then you just need another senior engineer like that. In my experience though group 1 is more common than group 2.
[1] There are irreplaceable senior engineers who have become so deeply expert in a particular technology you don't want them to do anything but own that code.