Hi Vern
On the trees, please check your antialiasing setting. In this case you may need to set it to maximum, as lower settings will result in different looking transparency (so as to improve frame rates).
On PBR ground textures, the bleeding/distortion will depend on the texture itself. The smaller the 'height' changes in the texture, the less distortion it will show on hard angles. OTOH, PBR textures can also be made with 'flat' height, which removes the issue entirely, but of course you lose the 3D height map effects.
Unfortunately Parallax Height Maps have no way to prevent this where the angle of the surface is beyond a certain angle (not sure of the precise amount sorry), and this is not just Trainz but for any games that take advantage of POM (Parallax Occlusion Mapping) for height mapping. The other option, in the current situations, is that we simply left that feature out which we did not feel would have benefited the community much. The big thing here is that it is a fairly substantial change to ground textures, and will require adopting new ground textures and new ground texture techniques to get the most out of it.
It's also not recommended to 'rotation spam' ground textures (ie rotating whilst painting). Apart from the performance impact that doing this has, the height map blending means that it won't look that great. OTOH TRS19 introduces 'detail maps' which help to break up the repetitive nature of ground textures (so visually it will 'repeat' over say 40 or 50m or possibly more instead of 5 or 10m), by changing the lighting on the ground texture, so rotation spamming shouldn't be needed (but you might find it good to blend a few different colours of similar 'low height' textures). It's still new, so I'd expect that not all PBR ground textures have this, but it can make a fair difference on ground textures.
IMO one thing that would help with this is a range of PBR ground textures with minimal or no heightmap applied, which is something I'm hoping to look at when I have time to make some of my own...
Regards