Parent on our team is an engineer and therefore a techie and he uses a Garmin Virb and swears by it. You have any experience with it?Smartphone does a pretty good job on the cheap. Generally it is your data source, which helps reduce a middle man piece of hardware. This is only for streaming of course. For recording, the GoPro is the best option, and for streaming/recording, the Mevo Plus is your best option. I'm still not a fan of the Mevo Start as the resolution is too small and has a fixed field of view. And on the Mevo Plus, unless you need ethernet or USB (for USB hotspot) interfaces, I wouldn't use the boost. The extra battery isn't enough to get you through a day, which requires external power. Externally powering the Boost creates a heat issue.
We are currently experimenting with using external HDMI to a streaming device with the GoPro HERO9 (using the media mod). Too soon to tell at this point, but pretty good video.