I'm sure the Hysol liquid adhesive added a decent amount of weight, but I never measured it. My rough guess was that about 2oz of the 10oz tent fly was probably adhesive weight. I'm really fuzzy on this now, but I think the entire tube of Hysol weighed about 3oz and I used most of it. Some weight may have left though as solvents evaporated...I'm not sure.
My guess is that the weight falls in between tape and sewing. The amount of liquid adhesive I was using seemed a lot thinner than tape does, but it'll never be as light as thread.
Using Hysol and then sewing later seemed to work pretty good. You just need to wait until the Hysol is totally dry or it'll gum up your sewing machine. It stiffens the seams a bit, but you could still probably do a rolled seam I would think. I've never sewn a seam after I taped it, but I wonder if the tape would stay fairly gummy for a while and thus be a bit of a pain to sew. Tape seems like it causes similarly stiff (ie. moderately stiffness) seams, but my guess is Hysol would work better if you're rolling and sewing later.
The heavier cuben variants (1.2oz and 1.5oz) are really amazing fabrics. For smaller stuff sacks (ie. pot sack, misc. gear sack) I would recommend using these variants because they are going to last forever and the weight gain is maybe 0.5g, which can often be offset by sewing it instead of bonding lighter cuben. You also want this strength for carrying heavy stuff. I've been using Zpacks Blast food bag for about 2 years now which uses 1.5oz cuben, and I've had that bag loaded with tons of weight (probably close to 20 lbs) and hoisted it up trees, dropped it, etc and none of the seams are visually stressing. For clothing and sleeping bag stuff sacks, lighter 0.51oz cuben is fine. I even use 0.33oz cuben for my clothes sack but that sack lives an easy life that is either in my pack or in my tent.
For most seams, I would just sew the heavier cuben using a simple seam. If it was a higher stress seam (ie. tarp ridgline, backpack shoulder strap attachment) I would probably fold/roll the cuben so that it's sewn through several layers. I think it's probably easiest and best to reinforce cuben with more cuben. Bonding on nylon might work, but sewing on nylon to cuben can cause trouble because the nylon has more stretch than the cuben. When you stress this seam, the nylon stretches and it ends up concentrated the stress on a smaller area of where it's sewn. My old SMD Refuge X tent had this probably with nylon reinforced tie outs.
That shot Ryan J posted looked like a lighter (ie. 0.74oz) cuben to me, but I'm sure you could do that to heavier cuben (or any fabric) with enough stress.
Here's a pic of the cuben tie outs I did on that tent fly last summer. It's 0.74oz cuben with the edges folded in and bonded, making it double thickness around the edges. Then I reinforced the corner with 2 additional layers of cuben (1 per side) by wrapping a piece around and the tie out is sandwiched between those layers. I ended up sewing this tie out later just because I couldn't think of a reason not too. But either way these tie outs are unbelievably strong...you could probably hang a truck off one :)