I just picked up my T/C omega. 50 cal. I understand I need to work on a load to get a good group. My question is "If I get a good tight group at 100 yards with approx. 100 grains or 2 pellets and it stays tight at 200 yards is this enough energy with the 2 pellets or 100 grains to make a clean kill that far, or will I need to go with 3 pellets or 150 grains ?

if your capable of the accuracy required you can kill a deer sized animal at that distance go right ahead but if you get the 3 pellet loads to work the more the better.

i have a omega i use 3 tripple 7 pellets and a 300 grain hornady sst it works great my groups run around 2.5" at 200 yards with this load.

If you are capable and have practiced, know where that load prints at that yardage it shouldn't be a problem. I have taken two deer over the last two years with a ML that were over 175 yards... I knew the yardage, had practiced at those distances, and knew where my load printed. Topped the heart on each one.

Agree wholeheartedly with previous comments. Just would like to add recent experience with MMP new(to me) sub sabot bridge wad or whatever they call it.
It helps tighten up groups when I push over 130 grains of FFFG Triple 7 powder.
It seems to smooth out the felt recoil too, although I realize that is not possible as recoil is not altered, it does feel a bit lessened.

I too would increase the powder charge over 100 gr. if routinely shooting in excess of 150 yards.