Exporting Mp4 For LED Displays

Hi Everyone

I am looking for some advice around the most optimal export settings for playback of Mp4 files on LED displays

take for example an LED display that has 768px wide by 584px tall, if we export an MP4 file with a VBR 2 Pass I'm finding if we use a target of 3 the file size is acceptable but it's blurry.

if we use a target of 14 it's clear the problem is the files size is getting a lot bigger.

What I don't get is sometimes if we're shortening a video supplied by a customer Premier Pro makes the file double the size of the original if we encode with anything higher than 4.

any advice would be appreciated