I stopped playing FO:NV because of glitches (finished the game but quit after that) but have returned via the Ultimate Edition. Right now I'm playing through the regular game (there are STILL glitches grr).

Eventually I'm going to start the various DLCs. Are there glitches or problems in the DLCs that I should prepare for or try to avoid?

Do you have Xbox Live? If not that may explain why your still explaining various glitches, I'm not sure whether all the patches came with Ultimate Edition or whether they relied on Xbox Live to update it for you.