Does the G7 output a 16:9 aspect ratio over hdmi?
I've only used Miracast streaming compared to a hardware solution such as MHL (HDMI out) or SlimPort (DP/HDMI/DVI/VGA out), which are the two wired mobile phone display protocols (so if something says USB-C to HDMI, it is really referring to these standards). However, when streaming wirelessly, a new bubble overlay appears (only on the phone) that lets you change a few options (such as changing the aspect ratio from 19.5:9 to 16:9, screenshot included as attachment).
If using the default video player, the audio and video will only be displayed on the device that you are streaming to and you don't have to worry about orientation (other applications such as YouTube will play the video both locally and on the remote device, although the audio is passed through). Hopefully using a SlimPort cable (see below for why I'm suggesting this) would offer the same bubble since mirroring/streaming would be activated much in the same way.
I don't have a specific need for streaming via cable (everything just gets ingested to my local Plex server), but for those looking for one, I would avoid using anything made for computer products (such as Apple MacBooks), as those ports may physically look at the same, but have a very different pinout (while it's unlikely that anything would explode, such adaptors are not meant for this - I've specifically seen a person try using a G5 and a similar, albeit older, Apple hub to get output and charge and the charging did nothing). In fact, I came across a nice bit of text on the Wikipedia article (
List of devices with video output over USB-C) while trying to figure out why this is working for some people and not others.
LG formerly supported DisplayPort on their
LG G series and
LG V series phones, but dropped support in the G6, G7, V35, V40 phones. With december 2018 software update LG enabled DispayPort output in G7, V35, V40 phones.
So it looks like we might still have horrible OS/security patches, but at least they threw us a bone here. If you already have an MHL cable from a phone such a Samsung or others, it will
likely not hurt to plug it into your phone => display to see if it works. As far as charging, HDMI provides nominal power (not nearly enough to charge a phone while in use), and this direct input to output lines are called passive cables. There are MHL lines with active cables (another cable is spliced in to direct I/O line to provide charging power) that have the possibility to cause problems, but again they either should work or shouldn't. I hope this helps, and feel free to post any follow up questions.