UI3 uses profile 0 by default. in blue iris options>webserver>advanced> steaming 0 configure uncheck limit bitrate or set it to something higher than the default 512, like 2048 or 4096.
What are the default settings for Webserver>Advanced>Encoder Profiles? I jacked my settings all up trying to get better quality stream of multi view (aka channel 1) in tinyCam just to later realize the setting for that is in a different location.
The encoder profile default settings are something like this.
Most web server streams use the Streaming 0 profile. Note that UI3 has its own system of encoder profiles which inherit some settings from Streaming 0 and override others. UI3 specifically overrides the bit rate limit and output frame size with each of its default profiles. UI3's "VBR" profiles additionally override Quality (20%).
If you want a better group stream (multi-view) then a big part of the puzzle is to find where you can resize the frame:
The default group frame size varies based on your camera layout but it is usually around 1280x720 or smaller, which sucks on a large display.