However I was put off by the fact that when the joycons being held sideways the colours would not match on each side and moments like this drive my OCD insane
Colours not matching? In which way? If it's the pairs of left and right, it's similar to the Neon Blue/Red, but you can get paired colours like gold. If it's the buttons, they are also optional (they come included but buttons are not part of the shell). If it's the railings, idk. The guy in the video had a green one, but maybe it's because he had a green Splatoon joycon to begin with?
I don't think they look too tacky. Heck, I only discovered these after being rather disappointed in knowing that I wouldn't be able to buy a pair of Official Red Joycons anytime soon (not sold in the UK and also out of stock for imports). So I spent some time looking at how people could mod their own. Some have painted them and put cool designs on them
https://imgur.com/gallery/jfaPV Can't blame me for looking elsewhere when Nintendo themselves can't provide.
The shell casings do look cool though. Very tempting

But Mahius, isn't the MHXX special edition have its own custom casing of sorts?
It does, the MHXX Switch has the regular grey casing, but the logo on the back is a MHXX Logo. Your preference for the shells over the joycons is interesting though. I showed my brother and he loved the joycons (especially the see through ones, a nod to GBA) but didn't like the casings. It still comes with regular grey joycons though and you know I want red ones... (hence my discovery of the above)
Today is the day, but unfortunately a busy day for me. It arrived in the country yesterday and was an additional £25 for tax and customs fees (via DPD), though that's nothing compared to the inflated price I paid for it to begin with. It was this or trying to find a Neon Switch and Neon spare joycons... which at the moment seems rarer than an SNES classic.
I probably won't open it for a while given that MHXX is the only game I currently have and I'm still playing the regular MHGen. Unless someone convinces me to get another game (my brother likes Xcom and thusly wants to play Mario + Rabbids).