Hi! Usually I just lurk here because I'm pathologically shy, but I want to help a fellow gamer so I'll try to get over my shyness and give as comprehensive an answer as I possibly can.
If I understood you correctly, you'd like to back the game but don't care much for physical rewards, right? If so, you can still pledge for the game at the backer portal, and from there you can select the tier you prefer.
Currently, all the tiers give digital rewards because IIRC the deadline for getting physical items has already passed.
The basic tier, ie. the less expensive one gives you a digital copy of Deadfire, an ingame item and a forum badge. The higher the tier the more digital items and stuff you can receive (artbooks, wallpapers, digital maps, etc.) and the more it'll cost obviously.
After choosing a tier, you can choose one or more addons (or none, if you're happy with what you're already getting) which are all digital too. Amongst these there's the possibility to pick the season pass fo future dlcs.
All in all, basic tier + dlc pass costs 55$: 35$ the first tier, 20$ the season pass (called "Pillars II dlc" in the menu where you choose it). Obviously the total will be more if you pick higher priced tiers.
TL; DR: go to the backer portal, click the "pledge now" button and from there pick what you prefer.
As for the voice acting, it's been stated that there'll be more than in PoE 1 but afaik we don't know how many npcs will be voiced etc. If someone has more info on that regard, feel free to fill in.