Don't really see the need for multiple pockets if you're planning on packing things in ziplock bags anyway for water protection. I find it handy to have a handlebar bag for items I want accessible while riding (camera, phone, snacks) and a seatbag for tools that I always want to have on the bike even if the panniers aren't (spare tube(s), levers, patch kit, multi-tool). Everything else can go in single-compartment panniers. I've been putting my camping gear in one (tent, sleeping bag, pad) and everything else (clothes, personal items, food, cooking gear) in the other.

Since you're not sure how much you'll be touring, I'd get some basic and pretty inexpensive panniers. Just make sure they have as much capacity as you'll need. If you end up touring more often you'll undoubtedly develop some stronger ideas about what features you'd like to have. So wait until then before getting any more expensive bags.