My rambling on the 8SL, excreted from my mind just for you:
Using the double-flanged tips is mandatory as the 8SL incorporates the resonant ear canal peak into the tuning, making the timbre sound like plasticky garbage (read: like the Solaris) without deep insertion, although the single-flange makes the soundstage very wide by IEM standards.
Overall sound signature is a more neutral-ish variation on the fun mainstream chi-fi V-shape (thin-ish lower mids, boosted bass and treble).
Bass is boosted above what I'd consider neutral but is on the low end of consumer mainstream. VX is what I'd consider neutral, which is difference #1. I actively avoid esoteric tunings that would make your non-audiophile friend complain about the sound being boring, so I personally consider that a plus. Bass quality is the meh you'd expect from BA bass, lacking the meaty, speaker-like thump and sub-bass rumble you get from DD IEMs or the U12t. It's not at the level where I can't recommend it for electronic, but the U12t's meatier bass makes it better for the genre. Upper bass is a bit muddy, too (by TOTL standards).
Midrange balance is Harman-ish, thinner-than-neutral lower mids but with milder upper mids, adding depth and removing the harshness for people who find the likes of Moondrop unpleasantly shouty. Some of the best midrange resolution I've heard, slightly less than the VX and U12t but ahead of the pre-2020 CA Andromeda, Moondrop A8, and Fearless S8P.
Treble tuning with lower treble dip + mid- and upper treble boost adds definition, but makes the timbre sound softer than natural (difference #2 from the sharper VX), though I think it's at still at a level where few people would dislike it, makes cymbal decay sound a bit too long, and adds an odd crispness at the top, though non-sticklers probably won't mind that, either. Audio quality is more dependent on the source music than with the likes of the pre-2020 Andros, U12t, or other chi-fi; you really want music with >10 kHz present. Upper treble might be a bit zingier than the U12t and can get fatiguing after several hours if you're listening to music that has boosted upper treble (read: modern pop).
Vocal balance: male vocals sound a bit thick and reasonably forward, pretty nice for rock, but female vocals sound more distant and lacking in presence than ideal because of the thin lower mids and boosted upper bass, hurting intelligibility a bit. Not bad to the extent that I can't recommend it for pop, though, unlike with the A8 where certain vocals seemed to blend into the rest of the music.
Stereo imaging isn't pinpoint like the U12t but sounds more natural, not hazy or blurry. Great instrument separation even by over-ear standards, though it still falls significantly short of the HD800S. Would very much recommend for orchestral classical. However, bass imaging has an odd forwardness to it, as if drums were ahead of other instruments. Soundstage has reasonably good depth and extends to 1.2 head widths to my ears; a benefit of the boosted upper bass. Wider than the VX, difference #3. It would probably sound wider to the average person.
Overall, I'd call it a safe all-rounder pick. I'd put it somewhere between A+ and S- on the Crinacle chart (edit: I don't know if anyone cares, but I'd rank U12t at S+, Anole VX at S/S-, A8 and pre-2020 Andromeda at A, JVC HA-FDX1 and S8P at A-, Solaris at B+, MH755 at B, FiiO F9 Pro at C+/B-. I guess I can recommend the 8SL if you can get it for the $750-$900 used rate, but not at MSRP unless money is no object for you or you really like its tuning, as you could just get a used U12t at $1400.
edit: There's a little bit of hollowness with vocals on the QDCs that isn't there on the U12t with its crisp lower treble, while the latter can get slightly more sibilant at times.