Recently purchased the furniture for my flat from Ikea, Danube, Bontrue etc., none of which have vouchers in gyftr portal. Since it's furniture for home, I am looking at ROI for at least 10 years, so didn't want to compromise. If you are looking for a similar ROI, I think you shouldn't be concerned about maximizing rewards.
I was rooting for HomeCenter because of vouchers. But didn't quite like the catalogue display at their showroom(high prices for sub-standard products).
Just my 2 cents.