Newbie question about modchip (ps2)

yes of cause you will be able to play back-ups that the whole purpose of a mod-chip.

The Jap/Ntsc back-ups will work but they will be in blk/wht unless you apply PAL patch to the game before you burn it back to CD.

Also as Charlie will tell you, you can buy a Pal to Ntsc converter for your T.V from maplins which will also do the job for you.