You seem to be using open pattern and V3 interchangeably but I think you’re asking for differences between the TC95 18 x20 and 16x19 patterns. In terms of arm friendliness, both are pretty arm friendly and you are playing them with gut mains and multi crosses so you’re hitting with melted butter
I only play full poly so keep that in mind. The 18x20 I’d play at a lower tension of around 42 or 43lbs (full poly) to get a string bed equivalent to the open pattern at 46lbs. The 18x20 has a more firm feeling string bed comparatively. Playability, 16x19 naturally hits a bit bigger and if you hit with heavy spin then a heavier ball. Both are great serving sticks and beautiful authoritative volley sticks. I also find the 18x20 requires a thinner gauge string around 1.20mm while the 16x19 plays best with a larger gauge string around 1.3mm. The V3 Angells overall seem to have upped feedback a bit. At the end of the day the choice between the two is dependent on your hitting style. If you are more prone to falter hitting then stay with the 18x20 and if you hit heavy top spin or like to interchange spin then get the 16x19.