The only new thing I'm seeing so far is the improved quality divots, and the more detailed and differentiated golfers. We're not seeing the new SpeedTrees yet, nor the new lighting. I haven't seen much new in terms of textures, but I haven't been able to spend a lot of time looking for that in the past few weeks.
I'm more excited for this release than I've been for their prior two for a number of reasons. I'm still playing TGC 2 because I like it's tempo dependent swing, and TGC 2019 looks like it will add even more dimensions to that!