I am trying to install Dragbody's sweet mod and my NMM is saying I need the masters for the file to work, and it says I require all of Fallout 3s .esm files including DLC. Also says I need TTW mod which also requires Fallout 3s .esm. Game instantly crashes upon start up. So my question is do I have to buy Fallout 3 GOTY to get this mod to work? Drags requirements say I need a copy of Fallout 4 and NV which I both have through steam

If you are looking to use the TTW version, then yes, you need TTW and a copy of Fallout 3 with all DLC. Not having them and still trying to activate the mod will lead to the game not starting due to missing masters.

TTW is a mod that aims combines Fallout 3 and NV into one single package so that players can visit both spaces in the same game, and also play FO3 with all the improvements that NV brings.

I do not use it due to incompatibilities, but if you want to try it out, here it is.

https://taleoftwowastelands.com/index.php?sid=3575367400cb6ac261be4e1ff4799d91

HOWEVER, it is perfectly possible to use Drag's mod without TTW or Fallout 3, but you need to use either the Standard or Compatibility version (not both) instead of the TTW version.

Fallout 4 IS NOT required to use the mod. In fact, having Fallout 4 makes no difference whatsoever because the mod already has all the assets it needs, it doesn't touch FO4's files in the slightest. I'm not certain why they list it as a requirement, maybe due to some legal thing since it uses modified assets from FO4, but I wish they wouldn't because it confuses a lot of people who are new to modding.