Shareable links to GG wishlist / GG collection would be great.
I've always found my Steam wishlist a bit redundant as friends often search price comparison sites anyway.
I would say though, if users share their wishlist with friends, with the intention of them buying them gifts. Then users should be able to set their DRM preference.
I would suggest this preference is just one global option, with perhaps the ability to change it on a game by game basis.