"All the twin time at ATP would help me get hired at a cargo copmany like ameriflight. I think??"
You need 1200 total, a little multi, and a connection, to get hired at Amflight, at least when they are hiring. The best thing ATP had going for it was back when regionals were hiring 500 hour guys and ATP could get you there in a year. Thankfully, those days are gone. Hopefully, for good. If 135 421 is your goal, I'd say get the CFI and get to 1200 hours. Then, do six months of 135 freight, where ever. Then, you are golden for the job you want as long as you network and make sure they know your goal is to work there.
Good luck to ya.