If you read through all of the topics and feeding lists on this site, and others, it is definitely overwhelming- and everyone does things a little differently. A lot depends on the age of your turtle. I think the general rule of thumb, and someone else can correct me on this if I'm off on my numbers, is if you are feeding a juvenile, they are slightly more carnivorous than adults, and about 40% of their diet should be protein. If you are feeding an adult, 25% should be protein.
For myself, I feed my RES every other day, or every two days. He gets 6-7 pellets twice a week. He eats a lot of romaine, dandelion greens, and I supplement with carrots, turnips, sometimes tomato, apple peel, or any other appropriate veges as I get them. And he gets to enjoy cut up grapes with the skin off every now and then. He also really like anacharis, which is a water plant, but I don't get that as often. I also make cuttlebone available for him in his tank. This is just my feeding schedule (my guy is about 7 years, by the way), and may not work or be agreed on by everyone. I am always open for improvement though.
IMO, I would think feeding twice a day is overindulging, but that's me. RES are notorious beggars and would eat all day if you let them, especially pellets- at least my guy would. We fed our guy too many pellets too often when he was younger, and as a result he has a minor issue with retained scutes because he grew too quickly, so I would do a lot of reading and get different input from other people on what they think about the pellet situation.