You have pretty much same PC as me.
You have 3.2 upload, I would assume that its stable ? Do you have in plan to stream online games ?
Anyways for less demanding cpu games you can use fast/faster preset with checked CBR and use 2500 bitrate and buffer 2500 aswel. The thing is, if you use fast preset with 2500 bitrate its gona be sweet and nice even in new games but cpu usage will go on 100% most likely and game will shutter, so for example Unity of Far Cry 4 with that CPU you can stream on VeryFast preset with 2500 bitrate/buffer. Keep on mind its got gonna look really good, but for your tests you can use fast preset and see how much performance you will loose but gain quality with same bitrate.
Famous rule for unpartnered channels is - Use your CPU more, bitrate lower to provide good quality and have watchable stream for everyone even with slower inet connections. Unfortunately new games are really cpu demanding so even one i7 4770k cant do both on FAST or FASTER preset, but on veryfast is working fine. That is why serious streamers have dedicated PC special for only streaming while they are gaming on second.
All in all, simple settings:
- 2500 bitrate / 2500 buffer - CBR checked, CBR padding checked
- 1280x720 (downscaled from 1920x1080 native monitor resolution I assume ?) - Bilinear downscale, dont worry about this.
- 30FPS for that bitrate, if you are partner or you can provide 3500 bitrate which is 3.5 upload then 60fps would be okayish for 720p. Also try using 45fps in games like Call of Duty / CSGO. 45fps feels exactly like 60fps on twitch, on youtube it will be recognized as 720p45fps instead 720p60fps (yes, that is the new option) and you will save little bit of CPU and stream quality and still provide pretty much same quality as on 30fps (instead using 60fps)
- Veryfast preset for really CPU demanding games, Fast or Veryfast for less (you need to test particular games). For example if you run BF4 on Fast level you might get input lag or even fps drops
If you have any questions just shoot :)