I've been doing 5/3/1 for 6 months. I also do kettlebells. On 5/3/1 De-load weeks, I do kettlebells
It looks like this
Monday Squats, Bench Press, Pullups 5/3/1
Tuesday Heavy Double 70 kettlebells Military Press and Row ladders 5 ladders x 1,2,3
Deadlift alternated with Double swings. 5 sets of 10, One hand swings 88 lb bell
Thursday Double Kettlebell Floor Press, Rows 5 x 5. Double Front Squats and Double Snatches. 5 x 5. I used 70's except on the double snatch. One arm Swings with the 88 as a finisher
Friday 5/3/1 Barbell Military Press, Deadlifts and pullups
So as you can see there is both 5/3/1 as well as some ETK influence. In my opinion, kettlebells are way more fun. But as a program, I like 5/3/1 more because of the squatting