Q.Will picking fresh grape vine leaves negatively impact the quality of grapes?
I have several table grape vines. We pick the soft newly growing leaves from around the tip of the shoot for cooking such as the stuffing (dolma). The favorite time for picking leaves is late April to end of June or all season if the vine is actively growing. The leaves are picked when they are about the size of a palm. What is the practice of picking leaves without impacting the quality of grapes? I still do leave removal when leaves become dense. But those leaves are too old or too hard to be kept for cooking.

Certified GKH Gardening Expert
Pruning grapes outside of dormancy is not recommended. This will negatively impact the production and fruit quality. HOWEVER, if you already know that you will be taking that entire vine off, then pruning from that vine will not be too much of an issue.
This article will help you with pruning grapes properly, which any cutting on the plant, whether it be for eating, or just pruning, will be considered pruning: https://www.gardeningknowhow.com/edible/fruits/grapes/prune-grape-vine.htm