I beg to differ. Other than spiffy clothing and learning some mussar, there is little in common. The greatest of the Slabodka talmidim, Rav Aharon Kotler, Rav Yaakov Kaminetsky,Rav Yaakov Yitzchak Ruderman,and Rav Yitzchok Hutner, all could claim to have headed yeshivas in the Slabodka tradition. In Slabodka there was no specific derech in learning (a quote from Rav Kaminetsky), and they certainly didn’t spend a whole zman on just a few blot. So to claim that Chofetz Chaim is a throwback to Slabodka is not true.
Did the students in Slabodka also go to college at night? No. Do they switch yeshivas in Chofetz Chaim every year or so? In Slabodka they did. Does Chofetz Chaim encourage their students to hear shiurim of gedolim in neighboring yeshivas? In Slabodka they did. Does Chofetz Chaim send out groups of boys to strengthen mussar in nonmussar yeshivas? In Slabodka they did. Besides, how many chess masters came out of Chofetz Chaim? In Slabodka it was what they did in their spare time. I suggest you read some books on Slabodka and yeshivas in Europe in general, you will see very little in common with Chofetz Chaim.