I tried making tweaks to my ini settings but everytime I load up the game they are overwritten by the default ini. Is there something I can do to fix this?

In short: there's a big .ini file clusterduck. I never bothered to use process of elimination to find out which ones actually need to be edited (as in, which ones overwrite each other), so here are all the locations:

Documents > My Games > FalloutNV > Fallout.ini
Documents > My Games > FalloutNV > FalloutPrefs.ini
Program Files > Steam > steamapps > common > fallout new vegas > Fallout_default.ini
Program Files > Steam > userdata > 39775384 > 22380 > falloutprefs.ini

My advice to you, is to start drinking heavily--er, make sure none of them are read-only and make your changes within all of those files to be on the safe side.

As a side note, it seems steam might "update/reset" the main .ini file from time to time. Happened to me at least once. So... be prepared for that.

EDIT: The location of the last file is subject to change--those were my numbers, they may match up, they may not. Poke around enough and you should find it.

Edit that one. That is the one the launcher will use when starting the game.

Any idea what purpose the others serve?

Other than for added confusion? Nope. Not sure why they didn't leave it as it has been since (at least) Morrowind but it's annoying. (Where I started the TES games. So maybe earlier.)

Thanks wolfpup. Your a saint.