Is Russian Warmblood an actual breed in horses?

Yes and no. A warmblood is as a general rule a description of any horse that is neither a hotblood (Arabian, Thoroughbred, or Akhal-Teke) or a coldblood (Draft). The majority of horses fall under the 'warmblood' heading. That being said however, many European sport horses are called Warmbloods, this would include the Hanoverian, Holstein, Oldenburg, Dutch Warmblood and many others.