Hopefully others who are more experienced in vinegar making chimes in. I have attempted to make red wine vinegar using Bragg's apple cider vinegar with mother several years ago. For my taste, it was very strong in acid and I did not care for it. But, I really did not understand how much further water could be added to dilute the acid without compromising safety. Like you, I am going to attempt making red wine vinegar again using one of the recipes from books I own now.
I do however make different infused vinegars using either apple cider or rice vinegar as base. Also love making infused soy sauce such as those infused with shiitake, garlic, green ume apricots from my yard, citrus peel, kombu, pickled umeboshi, etc.
Although it is referred to as ume vinegar, not sure if it qualifies as real vinegar. I make umeboshi pickles annually and must first keep ume with salt and sugar brine for a week before they are dried outdoors for 3-4 days. The liquid brine left is called ume vinegar in Japan and it is used for flavoring and it does have sour taste with amazing aroma that keeps lifetime like umeboshi and miso.