It sounds like you have this pretty much figured out, but for some reason I typed a wall of text.
When you have an album with a main artist and a few tracks where the main artist is joined by other artists, like on the Beyoncé album, we don’t want that as Various Artists, and when tagged correctly it looks like this
screenshot
mediainfo for Superpower
Complete name : /Volumes/Audio/Music/Beyoncé/Beyoncé/112 - superpower.flac
Format : FLAC
Format/Info : Free Lossless Audio Codec
File size : 27.7 MiB
Duration : 4 min 36 s
Overall bit rate mode : Variable
Overall bit rate : 840 kb/s
Album : BEYONCÉ
Album/Performer : Beyonce / Beyoncé
Part : 1
Part/Total : 4
Track name : Superpower
Track name/Position : 12
Track name/Total : 14
Performer : Beyoncé feat. Frank Ocean
Producer : Columbia Records
Label : Columbia / Parkwood Entertainment
Genre : R&B
Recorded date : 2014-11-24
Writing application : FLAC 1.2.1
ISRC : USSM11307809
Cover : Yes
Cover type : Cover (front)
Cover MIME : image/jpeg
MEDIA : CD
RIP DATE : 2014-11-24
RELEASE TYPE : Deluxe Edition
RETAIL DATE : 2014-11-24
RIPPING TOOL : Exact Audio Copy (Secure Mode)
ACOUSTID_ID : 760ba522-26af-41e2-aa9d-aca683e00c10
MUSICBRAINZ_RELEASEGROUPID : 8596171e-23b2-4bdd-8f1c-11960df0ecbe
ORIGINALDATE : 2013-12-13
ORIGINALYEAR : 2013
RELEASETYPE : album
RELEASESTATUS : official
BARCODE : 888750384423
ASIN : B00O87J9NU
ALBUMARTISTSORT : Beyoncé
RELEASECOUNTRY : XE
SCRIPT : Latn
CATALOGNUMBER : 88875038442
DISCSUBTITLE : Audio
ARTISTSORT : Beyoncé feat. Ocean, Frank
ARTISTS : Beyoncé / Frank Ocean
MUSICBRAINZ_RELEASETRACKID : 3abd3f9d-3a59-44ff-b809-6ed9a476d482
Audio
Format : FLAC
Format/Info : Free Lossless Audio Codec
Duration : 4 min 36 s
Bit rate mode : Variable
Bit rate : 838 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 44.1 kHz
Bit depth : 16 bits
Compression mode : Lossless
Stream size : 27.6 MiB (100%)
Writing library : libFLAC 1.2.1 (UTC 2007-09-17)
Language : English
So I’d hope you could manage something like the above for the Hardy track.
If you prefer it as Various Artists, though, it goes in
F:\PlexMusic\Various Artists\AlbumName\...
I use Various Artists for movie soundtracks and for live festivals that might have two or three artists on the recording doing seperate sets. I don’t like using Various for the London Philharmonic preforming various composers popular music, but it happens.
You have a very tricky issue with a Various Artist single, and so technically no album.
On top of that, Picard doesn’t even know of the single 
Anytime you move a file or change its name, you have to plex dance the album.
If you skipped that, it would explain the inconsistent cover.jpg behavior. There are a couple of other factors in cover art, whether it’s embedded into each track and whether you have Prefer Local Metadata enabled, and of course your tags matching where you placed it.
