Tying myself in knots a little to remember how this works, hoping someone can help me untie.

When using a GUF to upgrade an Avios redemption (upgraded at time of booking) from CW to F, will the cash component on the GUF’d seats (taxes, YQ etc) be that for CW or F?

If it’s F taxes, I’m wondering if it’s even worth using the GUF in this case, since Avios cost for CW and F are roughly the same (F even fewer off-peak), and CW “taxes” are under RFS, whereas F taxes are a lot higher, so would the GUF effectively have zero value in this scenario?

It would be a GGL joker redemption for 4 seats in F, with 1 or 2 Amex 2-4-1 vouchers applied, and possibly one GUF2 applied to 2 or the seats, if it saves me anything at all. Of course assumes there are 4 seats in A class to apply the joker. Wasn’t sure whether to post here or in GGL thread, but it’s primarily a GUF issue and not sure the joker part is relevant.

Thanks for any help.