1. Yes, as part of an interview it would be appropriate. Give each architect info on your project: photos, plans and a written program itemizing what you intend to add to the house in terms of space / function and any other goals or key issues. Write as much or as little as you like. Give this to them and schedule interviews. Ask them not to prepare drawings related to your project but to show some of their previous work or other images to facilitate a discussion.

My suggestion is that you ask them not to prepare any sort of drawings about your project because, in my opinion, they need to have a consultation session with you first. You want to get a more general idea of how they work and you want to hire an architect that is responsive to your goals and intentions....they can't do that until they have worked with you.

2. There is no standard fee structure for architects because many years ago the Supreme Court prohibited the AIA from issuing fee guidelines as a violation of anti-trust legislation. (The result is fee shopping....but I digress.) I can't recommend how to compare fee the structures you describe.....I will leave that to others.

Thanks Gill. From what it sounds like, I need to see who I get along with and whose portfolio I prefer, before asking for sketches of ideas. But it seems once I get to that point - asking someone to draw up ideas - then I've pretty much already decided who I want to go with.

Trying to decide on someone is tougher than I thought.

getshawnt - You might also want to ask someone you know about an architect/designer they've used and their experience with them. Don't know anyone who's used an architect? Ask your builder who they are comfortable using and why. Don't have a builder? Let people on Houzz know where you're located and I bet you can get a lot of recommendations.
As for rates charged - it's the same for interior designers. We all tend to charge a little differently from each other. Independent business people can do that and decide for themselves what will best support them and their family.
Keep in mind that the best job is not always accomplished by the most expensive bid, and the most inexpensive bid may not produce the results you desire.
Best of luck with your project.

Hire someone you can communicate with and through the review and consultation process you will find the renovation project you desire.
Or you could hire an architect with a strong portfolio and a clear design language that you like and put the project more in their hands to define.