The pre-order packs (Tribal, Mercenary, Classic, ... and what ever the fourth was) are the ones that just dump items in your inventory at the start. I always play without them.

Gun Runners arsenal adds very powerful and very expensive weapons you can buy from vendors, and also new ammo types that always come in handy, but it doesn't give anything for free.

Dead Money, Honest Hearts, Old World Blues and Lonesome Road are all large story DLCs, whose stories tie up to the main game's story, you should play them all.

Those do display pop-ups after the character creation, but after that they don't interfere.

Turn hem all on at the start. A few of them add perks that are nice options.

There are no problems with activating everything.

I always have them all turned on. Usually I put the gear I don't want in the dumpster near the store, or sell it to Chet outright. Gives you a little starting capital.

Same here. I view the Courier's Stash items as a way to customize my character's starting gear, to fit their particular back story.

Definitely start with all the DLCs turned on, They add a lot of good story to the vanilla game.

I turned all of the DLC on except Courier's stash. I can't stand when games dump tons of overpowered equipment onto a new character right from the start, so avoided that one like the plague.

Thanks for the feedback guys!

Very much appreciated.