Which quests from the first Witcher games matter in the second?
Solution 1:
An imported Witcher 2 save retains several items (see below), roughly 1% of your accumulated Orens, there are a few minor dialogue changes and free goodies depending on choices you've made.
Weapons retained:
Steel Swords
- Ard'aenye - (only available to saves imported from the original version of The Witcher. This item was removed from the Enhanced Edition.)
- D'Yaebl
- G'valchir
- Gwalhir
Silver Swords
- Aerondight
- Moon Blade
Additionally, Raven's Armor will carry over to a new Witcher 2 game if imported from the first game.
As for plot choices carrying over, there are three notable ones in addition to path selection. Spoilers follow.
If you saved Thaler, he will send you a letter when you get to Flotsam. This contains the Dragon's Dream formula. Additionally, whether you choose to kill or spare Siegfried (if neutral or siding with the Scoia'tel, see below for more details), and Adda affects some minor bits of dialog and plot. There are no mechanical implications for these choices however.
As for the critical path decision:
As noted, those that side with the Order in the first game can skip the sewer entrance to Loc Muinne that you're otherwise forced through if you align yourself with Iorveth - Siegfried hooks you up
If you sided with the Scoia'tel, Igor Vivaldi will extend a line of credit to you in Vergen.