There is no pre-installed application for recording calls. However, you can simply download an app from here: Play Store Call Recording to enable this feature. If you wish to record calls without an application, yes you can do that by adding your voicemail to a conference call. You should have an active voicemail to use this feature.
Sadly, LG G6 does not have LED notification light but it has a really great feature called AOD(Always on Display) which allows you to see your all the notifications on the screen without turning on the Display.
It also allows you to customize with the apps and clock style you want to see on the display.
You can watch this video for complete guide on how to turn on and customize the AOD on LG G6.