1) Since we are not the creators of such 3rd party addons, I suggest you contact the Quasar developers.2) Following Kodi guidelines, we are not supporting or discussinging addons related to illegal streams on our forums. Support ends here.
Seems my action was a bit premature.
Perhaps here you can find some help: Kodi Community Forum
What goes for Kodi also goes for LibreELEC. Addons that allow for streaming of illegal content will not be supported or discussed on our forums. So support will stop here.
Just FYI,
3) If those are video stream addon of the illegal persuasion, then we cannot help you.
1) A beep/static noise has not been reported by users, but someone must be the first one.
2) Wifi support is highly dependable on the supplied driver blob, mostly from Realtek. And they are unfortunately not the biggest fans of Linux.
4) A simple setting blowing up a USB soundcard? I'd say "never say never", but I doubt that would be the case.
I still wouldn't mind seeing the results of the 3 commands via SSH. 
For details or tutorials on SSH, see Accessing LibreELEC - LibreELEC
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Also, if you have a smartphone, you can use that too for SSH-ing into your machine with a proper SSH tool.
For another Windows machine, download the latest Putty.exe tool.
In Linux such as Ubuntu, just use a terminal session and go "ssh root@ip-of-gtx1070-machine".
NTFS drives should be identified as well, but Linux can be a bit picky. Drives need to be unmounted fully and correctly (also in Windows), otherwise Linux will not mount them. So when you exited a Windows session via a Suspend mode or something else, try to run Windows again, do a diskcheck, clear any errors, and do a full reboot.
Enable SSH in LibreELEC, and log in externally with root/libreelec . Give us the results from the following commands:
blkid | pastebin
mount | pastebin
dmesg | pastebinSure, just make sure the sources in the Kodi GUI are directed to the correct folders.
Cleaning a video/music library every time LE starts is a bit over the top. It will create more wear and tear on storage device, usb and sd devices particularly will suffer from it as the local databases are constantly being updated. IMO, once a month is more than enough.
Placing stuff on USB sticks was more due to the inital SD card corruption (which has become much less but is still possible) and the thought that USB sticks were faster.
SD cards are just as fast on a RPi box, or the speed difference is at least hardly noticeable.
If you want more reliable storage, use a HDD or a SSD (which has TRIM functions).
RPi defaults to not immediately create thumbnails (because of the slow-er hardware).
Also, Sandisk cards like others can have good read speeds, but mediocre write speeds.
And basically, don't compare a 35 dollar kid's toy to a genuine Intel pc in terms of speed.
I want a stable hardware.
Yes, don't we all?
Stable better hardware? What is your definition of 'better'? What are your other wishes in terms of video and audio? 4K, Dolby-ATMOS? And what is your financial budget?
I haven't had much issues with my Gigabyte F2A88XM mobos + AMD 5300 apu setups, although it's been a while since I ran OE or LE on them, since they are my file servers. It could be that MSI boards are more allergic to our "bloody edge" approach. I will try and run the latest LE alpha on them and see what happens.
Just asking the obvious question here: why use mounts via the system.d script, and not directly via the Kodi GUI ?
Also, if it worked okay a few days ago, what changed in the hardware setup department?
As always, complete log files are better than small portions taken by the user. It has more system info, and may point to the actual problem.
See HOW TO:Provide Logfile - LibreELEC
As far as the update goes, an error in updating is always possible. Hope you made a full backup before updating, otherwise, copy the old databases to a safe location just in case. Delete the new databases and restart LibreELEC for a 2nd upgrading attempt. If it still fails, there may be something wrong with the older addons.db, that wasn't noticeable in OE. In that case, install LibreELEC fresh, so you really have a clean start.
is there anything I should remove, things that are duplicated, redundant etc?
Nope, not really. LibreELEC itself is the replaced engine. Anything you have in terms of settings just be as applicable as you had with OE. If you moved from OE 7.0b3 to LE 7.0.2, all should be fine. If you move to LE 7.90.006, then you'll have the differences when it comes to Kodi 17 Krypton changes: new skin, new databases, etcetera. If the latter is the case, you will still have older databases, just in case the update to Krypton went wrong somehow. If all works fine, you can delete the older databases. Also make another full backup of the Krypton setup, it can always come in handy.
We are going to release LibreELEC 7.90.007 sometime next week, so you probably tested someone else's build.
Is your Odroid C2 waiting for a wireless network connection?
Windows speed tests are nice, but LibreELEC runs under Linux. That's a different ballgame. :o)
Hmm... It's a bug I think, unless the Kodi dev team has a remarkable explanation.
I always use separate files myself when exporting the video library. Then, I can also choose whether to export fanart and stuff. With the single export file option, everything just gets exported without asking. Hope they fixed that as well in Krypton.
But the single export option is weird. Example of the video library export via 'Single file':
Fanart in export folder: Airwolf:_The_Movie_1984-fanart.jpg
Movie in the NAS folder: /movies/Airwolf/Airwolf.hevc
Whenever I do an export via Separate files, fanart is exported correctly: /movies/Airwolf/Airwolf-poster.jpg for example.
I find that odd.
It's not so much a Kodi or LibreELEC problem, but more a Linux vs Windows partition problem.
The problem is indeed the colon character ":", Linux does accept the colon character in EXT4 file/folder names, and Windows partitions formatted like SMB/NTFS do not accept it.
So, the solution would be to manually remove all colons from your folders & filenames, cleanup your video library and rescrape the "new" movies. Or, alternatively, you could format your backup drive as an EXT4, but of course your Windows computer(s) won't like that.
Dependency issues can appear when programs are based on different OS versions, or builds, in case of LibreELEC.
That's why, we also prefer full log files, not just the part that the user thinks is appropriate. Full logs also provide for example machine info.