Interesting, I’ve never done a whiteboard challenge, and I’m not a fan of take-away home exercises..

I would say a portfolio review is baseline/could potentially answer what a whiteboard challenge is meant to suss out. But if there's remaining q's about someone's thought process/the team wants to understand what it's like working with that person, it could be valuable to do both

I’ve rarely done an entire portfolio review. Most companies ask for a case study of 1 or 2 projects. Whiteboard test is usually preferred over a take-home design test however.

I think it depends. Whiteboarding tells you how well the interviewee can collaborate with the team vs take home is if you want to see how deep they can get into a problem.