I'd replace the fg with the XPS; in some jurisdictions, fg is evidently not acceptable on the rims.

Caulking or foam to prevent block air movement. I prefer foam as it fills the voids better and insulates at the same time. Also, be sure to place the wall plates on a strip of XPS; this prevents vapour movement into the wood and keeps the wood and drywall above any future minor flooding.

Worthy, thanks for posting, I have read a lot of your replies and you seem to know your stuff. I was thinking the spray foam was best, but just wanted to make sure it would make a good seal between the concrete and panel.

Reading your link, it seems like the best way to do the rim joist is to cut a piece of XPS that will fit up in there and foam it all the way around. I imagine I will just reuse the FG and throw it back up.

After reading your other posts on the bottom plate, I was planning on doing the XPS underneath that already. Thanks for the reply

Why can't you use fg on the rim? My town requires it.