@Evilbunz
If you have The Witcher 1 Enhanced Edition, at least on Steam and on GoG you get like seven extra adventures if I'm not mistaken. They are NOT from the main story and do NOT take part of it. If you want to play those extra adventures, you have to go to de main menu, choose New Adventures and play one of the new stories.
By the way, five of them (Damn those swamps!, Deceits, Wraith of quiet hamlets, The Wedding and Merry Witchmas) are community mods, two of them (Side Effects and Price of Neutrality) are free DLC from CDProjekt RED I think.
Concerning the save issue: I think the only thing you need is to keep all the saves you want inside the folders in My Documents. The Witcher 2 only recognise saves from there, but I don't know if you have to keep The Witcher 1. I guess not, it wouldn't make much sense XD