I was in the same boat (sort-of)…I needed to do multiple tests and work to find the best quality for the content at the lowest file sizes. I can tell you that the 400 dollar CompressHD card revolutionized my life! Besides creating good looking transcodes…you can make several test files in minutes. So you can take their presets and if the file size is too large, just tweak it…then you can check the new file you create. h264 was a thorn in my side for many years…until I got this card, you’ll save 400 dollars worth of time in one week if you do a lot of h264 encoding.
As far as your specific issues, I’ve found what works for me by doing multiple encodes and taking notes of my settings for each one and determining what was working for what type of content. I do a lot of different stuff, soft – doc style, long dissolves, moves on photos…all the way to people standing at a podium for and hour. I can tell you that extending your GOP and reducing the bit-rate can save you a ton of file size on a podium piece, but you’ll hate the way it looks on more complicated stuff. You have to have sets of encoding settings to work with different content.
-Jason