Is the version of Morrowind that is available through the Steam/GameStop applications compatible with mods?

Iif I wanted to install e.g. the unofficial patches, or some small mods, say, LGNPC, or Alchemy of the Wind, or e.g. Wizard's Island or, say, Illuminated Order - would they work well with the Steam/GameStop applications and the Oblivion DLC?

Also, would tinkering with the modding tools, such as TESTool or TESAME, break the Steam/GameStop game?

Thanks.