I have a Tuff Country 2" spacer level (on top of the coils) on my 2017 Cummins and it works well. I got the one with the shock relocation bracket. It lets you run the stock shocks and helps maintain suspension geometry.
I've run this same product on 2 other 2500s (a 3rd Gen and a 4th Gen) with no issues. I'd say I've run them about 160K miles on those two trucks.
Between all 3 trucks I'd estimate I have run the Tuff Country producs over 180K miles.
Stock profile with 20" wheels:
With Level & 35s on 18" wheels: