is this from the turbo back ?

Yes

What type of muffler comes with the 5” stainless exhaust? What difference does it make going from 4” to 5” or why should I opt for 5” over 4” Do I need to install a tip? Also I’m looking for the quietest muffler with almost no power loss. Can in upgrade the muffler in a complete set up if it doesn’t meet my noise threshold.

Please read our article here 

https://www.dirtydieselcustom.ca/blogs/universal/4-vs-5-diesel-exhaust-systems-which-one-is-better

I have a 2019 ram 3500 diesel single rear wheel and I want a complete 304 stainless steel 5 inch exhaust preferably with a black tip because I have the night package on the truck

Please see part below

https://www.dirtydieselcustom.ca/products/2019-cummins-5-ss-downpipe-back-exhaust-system-flo-ss691?variant=31388599943204

Which muffler does this include

This will include Flo Pro's flow through design muffler

Will this fit my 2017 3500 crew cab with a 6-foot box?

Absolutely. As long as your 3500 has a Leaf Spring or Coil Spring setup, there won't be any fitment issues.