There is only 256M of GPU memory available on RPi, the most of which is used by other applications. There are applications (e.g. NewPipe in F-Droid), which can stream YouTube videos very fast, but it also depends on available media codecs and overall system performance. I wouldn't recommend you installing GApps at all, as they may slow down the whole system.
If you have a big project, please let us know and we will check on additional codecs or similar.
