I’ve been vegan close to two years, vegetarian for ~5 years before that.
To be honest, I don’t feel “completely rejuvenated” or amazing all the time or anything else that’s super out of the ordinary.
However, I do feel my diet overall has improved substantially, in that I eat far more whole foods, fruits/veggies/legumes etc. now that my meals aren’t completely centered around meat and/or dairy.
That’s not to say I don’t eat junk food or processed food from time to time, because I definitely do. Overall though, I feel the healthiness of my meals (which make up most of the calories I consume) has gone way up.
I take a b12 supplement, as should most athletes, vegan or otherwise. That’s the only supplement I take. For reference I run about 50-55mpw while working full time, am not an amazing runner but have run in the mid 14s for 5k while vegan, and had a college teammate who has run an 8:3x steeple on a vegan diet. It’s good for you, folks.