hi, I just realized that I bought this game for free on origin like in october 2014, but since the DLC costs around 11.96 during sale, I don't see a point of buying it on origin. Unfortunately the ultimate editions is not available on my region on steam so I am planning to buy it on gog in the future.

I am planning to play the one in my origin, however would it be possible to transfer it later to the gog version?

Yes, your Origin saves will work with the GOG version.

as long as you have the same mods installed yes the saves will sync to gog version... actually they will try to sync anyway but you can't play them without the mods they were made with

also gog allows you to have Da:O installed on more than one machine so always sync the local copy if asked [see screenshot]... this adds your local saves to the list of options but does NOT remove different character saves unless they have the same name