First of all, let m say, @Philreedshikes speak with heap plenty straight tongue (as does @REI-JohnJ for that matter). i think you have the size range down correctly, and a lot will depend on the season , terrain, and objective of your trip.
Iam currently very fond of my newest pack, a Traverse 37, which I have been using as a day pack, but which will easily work for an overnighter in decent weather. I can probably squeeze in enough stuff for an additional night, but that would be about the limit.. You might want to consider something with a bit more space, but you can achieve a two night trip quite handily staying within the 50 liter limit,again depending upon your gear necessary for the specific trip. I like a commodious day pack, because these days I am usually out prospecting for fossils (specifically the bones of the Channel Islands pygmy mammoth) and a successful foray means I will be returning with a bigger load than that which started the day.
Do follow the advice to gather your gear and measure its volume and weight. Give careful thought to the utility of each item. Is it necessary? Are there alternatives which are more versatile and perhaps lighter? In any event, obtain a pack with slightly more volume
Don't worry about appearing to be overloaded. What you need for your circumstances is what you need. If you are with a group, mutual savings can result from thoughtful planning to avoid unnecessary duplication.
Best wishes for your quest. There are lots of very fine packs out there and there is at least one, probably several, which will fit your needs. Good luck at just stopping with one or two. Welcome to Packaholics Anonymous....
one or more gifts or other benefits from the co-op.