I have experience with the KBD8X MKII. It's a good board, linears and tactiles can sound thocky, depending on plate.
One of the advantages of the KBD8X MKII these days are the aftermarket offerings for it. I have an aftermarket plate on mine, 2 more plates from a different manufacturer, and there's another place offering them now.
It's fairly robust, I hear of people soldering and desoldering theirs dozens of times, although I would never try that. It's a stable build that benefits from good stabilizers. Although you could create a pretty overly flexy typing experience if you opted to use half-plates, especially polycarb.
Mine has a polycarb full plate, a high-quality one. It's great for tactiles. I hear the stock KBDFans polycarb plate is pretty mediocre.
The polycarb casing option is extremely amenable to letting light out of the case. It can be set to extreme levels of brightness, if desired.
There are now aftermarket PCBs that are compatible with the KBD8X MKII, so it should be possible to mod these boards for a while going forwards.
Anyway, I can recommend it for people that like building and modding. Only downside, for me, is the lack of adjustable feet.
I also have an XD87, which I am typing on right now. I am put-off by the wrong-facing switch orientation. It's not an issue for me right now, as I had always planned to use the board with OEM-profile keycaps. And I'm using ART BOX switches, which are supposed to be ambidirectional. But I think that the switches feel 'tight' and more constrained in this board, like they're being compressed. Makes these Browns feel more tactile than I expected.
The spacebar sounds decent, I am using C3 V2 stabilizers here, and they work great with ABS.
But this is overall a very, very entry-level board, with fewer of the features that higher-end boards [like the KBD8X MKK] have. I'm not sure if it has QMK [mine is stock ANSI, so I never tried]. The plate seems to be a heavy chunk of iron or something. Alum, I guess. Wrong-facing switches. Don't get me wrong, it works fine and is fine for like the $60 it cost, but that's the tier that it's in.