I have never used a double sleeping bag.  I would agree that it is worth thinking about the weight.  Is one person going to have to carry the double.  Also, if I recall, thee are some sleeping bags that can be unzipped and two of that same model zipped together (to make a double).  But, in any case, have you gone to an outdoor store 9retailer) like REI and checked out the sleeping bags?  maybe you can find a store that have those and can both try them out before considering a purchase.

On tents, again you might check the outdoor retail stores to see about the tent choices.  Certainly ZPACKS has both the Duplex and Triplex which are very light.  But, they are pricey due to being made from Dyneema.  There are certainly lots of choices in tents.  Like also mentioned you have the Big Agnes Copper Spur UL3 (Big Agnes does not appear tot make the 2 person version any longer).  Then, you can find choices by REI, MSR, Nemo, Tarptent and others.

Also, you could look at websites like Outdoor Gear Lab (outdoorgearlab.com) for reviews (and there are others sites as well).  I don't know off of the top of my head if they have reviewed doubles sleeping bags.

Good shopping and enjoy