I have not optimized any of this foliage further than what is shown in the video so this could still be improved. I just wanted to show the tips that have helped me the most with Nanite foliage. I painted the trees more densely than is necessary for the video just to illustrate the viability of doing this.
I made the trees in Speedtree, which you can find here:
https://store.speedtree.com/
And for the grass in the video, I used the Megascans Grass Pack which contains fully modeled grass, just needs to be set to opaque instead of masked:
https://www.unrealengine.com/marketpl...
I'm terrible at tutorials but I hope that this info can help someone out. I'm running full Lumen HWRT with TSR in the video alongside Nanite.