I am with Tarptent, so keep this in mind.
We have a 26oz shelter called the ProTrail.
It is pretty much a shaped tarp but fully enclosed (if you zip the mesh inner door up).
If you add the weight and size of the tarp and a bivvy you will find the Pro Trail to be very competitive and does allow you to move, get changed, read inside and be bug protected.


https://www.tarptent.com/protrail.html