on a17.1 texture streaming is in the game, but there is no user options to enable/disable it, and it is default enabled.
ravenhearst and hdhq together was too much of a beast, so the texture streaming kicked in and created blurry textures in some places.
on 17.2 you can disable texture streaming, but 5.1 does not have a built in hdhq option.
for rh v5.2 whenever it is ready, you will have the option for hdhq again, and also to be able to disable texture streaming via the game.
we find in testing disabling the texture streaming with rh and hdhq enabled, brings memory use up to near where it was in a16, so some systems may struggle with it. i'm personally on a mid range system (gtx970, amd 8320, 24g ram) and run it great with it disabled.