I always found old style hardtail BB routing (1 outer from shifter to downtube, 1 outer from chainstay to mech) to be fine especially with a front routed mech like shimano shadow or sram, it’s top tube routed I have trouble with. (or is this some FSer with BB routing and lots of short sections of outer?)
You only said you replaced the inner, I always replace the outer at the same time aswell, a nice clean inner will soon get gunked up by old outers.
But yeah full length outer can help, specially with FSers
Don’t remove the “transport” grease from your chain, I was advised to do this in the past but sheldon set me right (see factory lube)