not read all the posts but heres my thoughts and some things to think about ...
bivvy bags are ok in good weather, or for cave camping, if you get caught out in a storm your either outside in the rain, or inside the bag where you are very restricted, unless you use a tarp, then the weight goes up, you cant beat a tent in my opinion.
hooped bivvy bags such as the Rab Ridge Raider are great, and ive enjoyed using mine, but i sold it because as i said before i prefer a tent, because i like the ability to move around, use my stove etc.
i once wild camped on cadair idris in my RRR, and the wind was so strong it pressed on the side of the bivvy, compressing the loft in my sleeping bag, so i got really cold with the wind chill, this would not have happened in a tent where the bag would have stayed lofted.
i bought a Dutch army hooped bivvy bag before the RRR, it was great for stealth camping, camoflaged, with a nice long zip making entry and exit easy, and huge, i could fit all my gear including rucksack inside with me out of the weather,
definitely worth considering if your not bothered about the weight, but it was heavier than my tent.
it all depends on why you want to bivvy,
if its to save weight, then a bivvy like the Alpkit Hunka might be worth a go, but not much comfort on its own, so adding a tarp ups the comfort, but ups the weight, or you could use a poncho as in the video below.
in my opinion a tent is a much better option, and more storm proof if you need it.
its a question of how light you want to go, as opposed to how much comfort you want
the lighter your pack, the more miserable you will be, we carry a few home comforts, like a chairs for instance, not only usefull outside the tent, but we use them inside without the legs to lean against giving us a nice level of comfort,
as most of you know me and April go out in all weathers,
i carry a 2 man tent its an MSR Elixir, its not the lightest of tents, but it suits us because it gives us a great level of comfort and liveability, without being too heavy to carry,
you can also pitch the inner only for stargazing, but we never do
and at £200 you cant beat its value for money, its a great tent,
has 2 doors and a footprint is included, we pitch the fly on its own to use as a shelter for lunch in a storm, and even sheltered under the footprint once, when we got a sudden heavy downpour, we laughed as we watched another couple getting soaked ...
Hunka bivvy bag and poncho setup
https://www.youtube.com/watch?v=diIPSE0JqtgDutch army bivvy wild camp
https://www.youtube.com/watch?v=34j23kMvNpsHTH ...