Yes, its easy to exist.
However, a pterosaur wing will use their superior limbs. Take in consideration Human inteligence evolve due the able to make tools. I'm not sure how this animal would evolve some kind of high inteligence without an opposite thumb. Unless than - this looks like weird - they use their inferior limbs to use tools, as the Dug specie from Star Wars.
Since they fly, is more probably they have a long tail to bring stability rather than a short one.
All this said, your angel creature would evolve from arboreal monkeys from American continent, with a long phehensile tail. Jump between different trees provide the pressure to appear one membrane between the limbs, as in the flying squirrel, and in the successive generations superior hands convert into wings.
Evolutinary pressure to inteligence is kinda hard to compare in this way. We can see capucchin monkeys with a justice sense, and use tools like stone age humans. Crows are master of logic, even without an opposite thumb, as show here and here. Since your angels will evolve to similar human face is easy to make they evolve to facial expressions and complex language, that are important steps. One other important boost in inteligence evolution is use of fire to cook food: more calories per portion, no demand all awake time of day hunting for food and soft food demand less strong teeth, opening room in the head to one brain expansion.
Your angel-monkey will demand one giant amount of calories to movement and metabolism, then the use of fire will provide a boost to improve inteligence without, although, they be smart enough to compare with humans. Issues in use inferior limbs instead superior limbs probably its a good reason to no evolve high as humans too.
The japanese macaque is the only (only I know) specie with white fur. This happen cause snowfall where they live. I cant wonder another good reason to one primate evolve white fur or hair beside it, even hominids no evolve white skin before explore northern regions. Highlands are a good bet too. Like humans, its easy build the specie evolving in a tropical region, expand to tall trees florests where fly evolve and after explore high montain regions, like the Amazon - Andes region looks like. White fur and hair will happen there, with brownish hair as recessive gene happen in some individuals.