Varget is a good choice. You want to use powders like 4064, RL-15, W748. It has a slower twist than what I see on other 7mm's at 1: 9.5 as opposed to 1:9.25 so it should do well with 120's but I would lean toward 140's.
G David Tubbs brought that caliber into the mainstream during the late 80's and early 90's when High Power Silhouette was more popular and he shot 120's on Chickens and I believe Javelina and moved up to 140's for Turkey and Rams. His goto powder was IMR4064 about 43-44.5 grains. In my experience the only bullet I shot that did not group well in my Remington 700 (1:9.25) were some 140gr PMC softnose bullets. All others from 100gr Hornady up to 168gr Sierra HPBT Match show well under .5 moa. With the 20" barrel I would lean more to 4064 and RL15. I always used CCI BR primers.