Picking a bullet grain for your rifle is not as important as picking a bullet length. While bullet grains and length are somewhat relative, its the length that determines how many RPMs are needed to stabilize the bullet. You have an 8 twist barrel. Pushing bullets faster has more RPMs and slower bullets have less RMPs. Heavier bullets (longer bullets) have slower muzzle velocities and, intern, less RPMs. Lighter bullets (shorter bullets) have faster muzzle velocities and more RPMs. We cannot speed up the heavier bullets because of chamber pressures. This pushes us into the lighter bullets for better stability.
Check out burger's bullet stability calculator here -
bergerbullets.com/twist-rate-calculator/ The 153gr in a 6.5 Creed will likely have trouble becoming stabilized with a 1:8 twist. I believe these bullets were designed for the faster 6.5 PRC.
The 140/139 and 147s are the heavy range for the 6.5 creed and you'll have to make sure you can push them fast enough with your rifle. This could require some experience at reloading to find what powder charge your max pressure occurs with test firing. A lot of guys run the 140 and 147s with great results and success but have the experience at reloading.
For a new reloader I would suggest the 130 range. These will stabilize well and the powder charge can be below the max pressure with good results.
If you listen to Frank Galli's podcast he talked about the 140 vs 130 in 6.5 creed a couple times. His
real world data has the 130s having less drop and less wind hold than the 140s in the same environment at 1100yds. The higher velocity of the 130s is helping acchive a better BC then the slower flying 140s. Here is the Everyday sniper episode (249) -
episode-249-heavy-bullet-vs-light-practical-application I shoot 130ELDs in competitions and have had great results. Just this weekend we shot 1425yds in a match and I was closest to hitting the target in my squad. (no one hit it all day)