There should not be any issues when two different solid state drives are installed in one computer, The Samsung 850 EVO models will not hamper the performance of the 850 Pro models. In fact, some technical reviews suggest the 850 EVO may perform just as well and sometimes a little better in synthetic benchmark tests. Most consumers and gamers will not notice any performance difference during routine mainstream use. A very heavy workload would be required in order to notice a performance difference. The vast majority of users do not do anything involving a heavy workload.