It’s actually quite hackish to do this on top of 1.0.1 (several files need to be changed b/c of bugs).
The recommended way is to use the current master (or upcoming 1.2.x), where this has been fixed.
You will get env infos automatically in your loss or postprocessing function (if these functions need this field, i.e. access it in a test pass).
Documentation is in-flight (doc PR is in review).
Yes, the speedup on Atari for PPO was ~20%. For more “learn-heavy” algos (lots of updates vs action inference) like DQN or SAC, it’s not really faster, but definitely not slower either.