issue 1. bitrate-Constant:
I wanted to output 24M when the original video was 22045, but it ended up with 5633.
I also tried outputting the same video at 40M and 60M, but it came out at 5600.
So I randomly tested IRIS and PORTEUS, NYX, and GAIA with 31 files of 1 minute or less, only the same settings allowed the bitrate to remain constant over 20M. Most of the results, I got a lower bitrate than originals.