Kanon's Silent attack makes it so when you spam Bern's Meta Super, you will gain a meter every time you use it while the opponent gets nothing. Their abilities are both the same in being the longest in the games, so you get the max length of each.
410's Break Boost drastically increases guard damage, making Bern's Meta Super much easier to guard break with and makes her dumb zoning much more of a threat. They both last the same amount of time so you get the max length.
Ronove is a good partner because of general stuff, like Ronove's high health which makes up for Bern's squishiness and his ability, which will increase the damage of Bern's meta super if it gets a CH. Rono's ability is pretty short though, but the amount of time metaworld is extended gives Ronove more time to set up his own meta supers.