Pixelhate

Yes this is normal, grass placement is done at runtime by the engine.

In NifSkope: https://www.nexusmods.com/newvegas/mods/76374?tab=files Part 06A, B, C In Blender: https://www.nexusmods.com/newvegas/mods/76324?tab=description

Yes.

Furniture will crash if TextureSet is used. You need to make a new nif with the new texture.

https://www.nexusmods.com/newvegas/mods/38153

I can only concur with what MadMongo said and suggest you to have a look at https://www.nexusmods.com/newvegas/mods/76374 to get the basic of a nif structure.

Does checking "Persistent Reference" help?

Also make sure to use the Geck Extender. (Hi MM )

Answers are in Bits of NifSkopery part 03B

NVAC just tells the game to not crash, it does not fix anything, so you have to live with any side effects of game not crashing when it should have. So it will allows you to play with a bad conflicting mod list by preventing crashing till game is unplayable or save is corrupted beyond repair. On the other hand, it will prevent a correct set up to work flawlessly. That's why it's not recommended anymore in those guides. That said, if you plan to make a play-through with mods that are known to cause crash and have no fix, NVAC is a must CASM is replaced by fucntions found in Stevie's tweaks which is a must have. https://www.nexusmods.com/newvegas/mods/66347

This is the place to start any serious setup: https://vivanewvegas.moddinglinked.com/intro.html

Pl is indeed very heavy on perf. I believe RoyBatty has done some scolling work on Pilgrim's landing in TTw, at the engine level it has been discovered that water has a major impact even if invisible, I remember someone doing some optimization work on the tree nif, probably some attempt has been made with occlusion planes as well. Despite all this PL still is very heavy and it's not totally clear why to this day (blame Bethseda). I don't want to discourage you but seasoned Modders have tried to tackle this with only a little fps gain.

Image courtesy of MacIntroll

The way it's already done in game with fake elevators, for instance, is like how it is done in movie: the player will be in a fixed environment with some windows/see thru and the whole decor around would be moving.

You are very welcome! I see people using the very last version or the ones just prior but I see also a lot of them having issues with it (especially with collisions) because Niftools aren't updated as fast as the Blender versions. The best place to find the latest Niftools development would be the Discord Nifmania https://discord.gg/3tCn572S Even if it's regularly mocked, I still use 2.49b without problem but I'm old school. Discord has become a standard in Modding communication, many little fixes & patches can also be found over there. I can be reached there as Pixelhate and I would be very happy to help you find your marks again if you want it.