Stepped headers are a bridge between tube sizes and how each straight tube size normally works. Dyno operators and engine builders see this all the time, straight up one size headers perform a certain way and the stepped headers slightly different.
When stepped headers came out, they noticed (build dependent) ether increased low end torque over the larger tube header or more top end HP over the smaller tube header but not really giving anything up on the other end.
The tti header is an excellent street or street strip header. The 1-5/8 - 1-3/4 is an excellent choice.
A move to a straight 1-3/4 header should be a beefy engine I order to be the stepped header.
To effectively use a 1-3/4 header to out power a stepped header would be more strip minded type of build where low end torque is of Absolutely little to no concern.
But, IMO, that would be silly to do. I’ve run 1-3/4 Hooker super comps on a 318 just fine. The power difference is seen only on a dyno or track. Driving in the street, you’ll never know the difference.
