So after the last couple months, my cliff notes as follows:
-The truck runs great even on a 30hp tune, I cannot complain about the engine one bit (I only complain about the slushbox 68RFE and my 3.42 gearing if anything).
-Maybe I would have spent the extra on the power levels and maybe run 60 hp as well as 30 to see which got better economy overall, however I wanted to go as easy on the 68RFE as I could so that's why I stuck with 30hp tune only.
-No regrets about doing the EGR physical delete, grid delete, or the GDP parts to relocate the heater to the throttle valve, as well as their intake horn, the engine bay is cleaner and I am not a fan of leaving parts in place that are not being used.
-Its a big investment and I only did it after my truck was paid for, and I knew based on inflation etc I wouldn't be going to buy a new truck any time soon, or had any plans on trading it in - My bumper to bumper was also up so I wasn't worried about that.

If I had a year old truck with 21k miles?
-I would dial it in with cosmetic mods such as tires, wheels, suspension first, and pay it off.
-You have a 2021 so you already have CP3 as far as I can tell.
-I would get the MM3 tuner, Flo Pro race pipes, and a 30" FTE resonator and call it a day, EGR stuff on the back end if you want to go for that.

But honestly, since I didn't see a wow difference in mileage etc, I probably would be a bit hesitant on a 2021 to throw all the money at a truck still under warranty, especially if it wasn't paid for.

I probably lost more mpg from leveling the truck than anything.

When it was first new and bone stock on 33" tires I saw an easy hand calculated 20-21mpg, about 22mpg on a trip to the mountains and back.

Hope that helps, if I can answer any more Q's let me know.