Bitrate - 3000 is fine. You can go higher, but not everyone got that fast internet like you. Think about people who still use DSL.
Resolution - native resolution for your game, usually 1080p and downscale to 720p. 30FPS is fine, 60 - if you want and if your hardware can go this (keep the game @ 60FPS and enconding at the same time).
1080p 30FPS is possible, a bit higher bitrate will make it look good - but this is pretty heavy, just test it - what ever looks better for you.
Usually you want 2 scenes for LoL, one with the window/monitor capture for the desktop client and one with game capture for the 3D client.
Think about the SceneSwitcher plugin that can change your scene when you start/close your 3D client.
Anything else like x264 preset, maybe using Quicksync and other things - just test it.
You can do local recording with OBS, it will use the same settings that are used for livestreaming - so you dont have to go live just for testing. Record some games with different settings and look what will work better with your hardware.
Your internet connection is fast enough to handle it so dont think so much about it.
