I want to use 168 nbt or amax.
I have lapua brass.
gun is a ga precision accurized remington 700 ss 5r.

I have the same rifle,Varget works well with the 168gr and 175gr matchkings.Be aware that the Lapua brass will likely produce more pressure than Winchester brass.I had to reduce my powder charge 3 full grains from the load data printed on the Varget container.

yes i see the same with w748.
i hunt short to long range, looking for a deer sized game bullet.
the combined tec @168 with win 748 shoots around .75 groups.
shoot a factory box of hornaday 168 match (2700fps) 1/4" to 3/8" groups this is outside the holes.
with a 11-1/4" twist should i use heaver or lighter bullets and at what fps?

Every gun is an individual.Shoot whichever bullet weight is more accurate in your gun.I am still deciding between the 168gr and 175gr matchking,but I want to try both a longer ranges this spring before making a final decision.I will shoot them at whatever safe velocity is most accurate.

I would also try R-15, IMR 4895 and Varget with bullets from 155 -175 gr in the .308. It makes a great paper puncher but fails to have enough steam for deer size game out at 500 yards and beyond in my opinion. I have used more R15 and 168's running at 2700 fps myself.