There's a lot of stuff there that will raise some controversy :-) A quick search for poppers will give you a whole range of different opinions on roasting results from standard & modded poppers - have a look back through the archives - there's nothing new under the sun!
In the end - if you are happy with the taste you're getting - excellent! Why fiddle!
However, there are a lot of popper users (i've only really poppered a few times out of interest - for $2 at the tip shop why not!) who go to amazing lengths to stretch out their roasts - so there must be something in it. On a cold day I got some 50g/15-20min roasts from a standard popper and the results were great. Faster 5min roasts - not so good IMHO. But I'm also used to the flavours of 18min roasts in a corretto.
With the bags? Cool 'em, seal 'em up, let 'em rest. The valve will release the CO2. If you can wait a few days to drink, the results in the cup will just keep improving.