Yeah the Terrain LOD Redone one is another strange thing. Might just be coincidence. I use the authors other mods Majestic Mountains and Blended Roads and they're awesome. I do also use BethINI with the recommended tweaks, I just turn the shadows down a notch.
I use the SE EVT version with the LE EVT aspens because the LE aspens come with the hybrid 3D LODs.
I think I may have found the problem. I'm not sure if when you go into free camera mode that it loads stuff outside your current cell/ugrids, but I just turned it on outside of the Solitude main gate and flew over to Morthal.
Pretty much all of my pine trees are full model with no animation. No wonder they transition so well . Although some of the snowy pines do have 2D trunks.
I can get all the way to Dawnstar before the trees start flickering between full model and 2D billboard. I honestly thought that SE EVT came with the hybrid LODs, but maybe not. I will re-run DynDOLOD at 1024 instead of 2048 and see if that makes any difference. If not, I'll try LE EVT again. I don't think I can go back to 2D after seeing what 3D looks like.