Any chance you can expand on your concerns re Argon cases? I love mine, the form factors is a big win for me.
I see users "loving the case" but having issues with internal physical connectivity within the case which gets blamed on software, and a general lack of good softwaer support for things like GPIO buttons, e.g. it works in Py2 but not Py3.
Hardware deinterlace is in private testing. 3D support is nowhere on the official priority list but one of the Pi devs is a 3D fan so it will probably get reimplemented out of self-interest eventually. Software optimisation for HEVC is unlikely to be reimplemented as it was. Most of the tricks required will be hard to upstream and this time around (after 9+ years of learning the hard-way what it means to maintain downstream forks) the goal for the Pi Foundation is to upstream everything. I'll never say it will be never be done, but I think it's unlikely and best case, it's going to take a large effort over a long period of time to happen .. by which time a large percentage of users will have upgraded to new hardware.
It sounds like a skin that needs updating or tweaking.
WiFi or Ethernet? .. If WiFi it could be a rubbish and slow connection. There is no normal need to fiddle with cache settings.
The "TV" link is a link to DVB/PVR functions (e.g. DVB card and TVHeadend). Add-ons like Arte/FranceTV will not populate EPG/guides there.
Put the Kodi GUI in advanced or expert mode and the settings shouid be visible.
The majority of issues with RPi4 are due to bad PSUs, bad cables, Argon cases, users not reading release notes that detail differences between old and new ways of doing things and/or having fundamentally wrong expectations to start with. Plus Halloway comment on the nature of support forums being full over users with problems is also on point .. it's the reason a support forum exists 
I'm running an RPi4B as the family "daily driver" without any hassles. For me LE10 is miles better than LE9.2 due to more features (HDR, HBR audio, etc.) and the only problems I occasionally encounter are 100% due to my own experimental changes in a self-built image.
NB: be aware that RPi4 support for 4K is limited to HEVC, not H264 .. we've had some animé fans expecting miracles with 10-bit H264 content.
Keep Kodi at 1080p "Desktop" and enable the whitelist with 3840x2160 @ 23.976/24/29.97/30 and 1920x1080 @ 23.976/24/50/59.94/60 with "Adjust refresh" set to start/stop. Make sure the Pi is connected to an HDMI 2.0 port that supports HDR/Deep Colour. If you want to play large filesize media you should use Ethernet, or be perpetually frustrated with the issues that come with WiFi connections.
Worst case .. stop Kodi and rename /storage/.kodi to /storage/.kodi-old and then restart. You now have a clean install. You can stop Kodi and move back things you need (sources, thumbs, DB files, etc.) but redo add-ons .. without tubed.
FWIW I have both YouTube and Tubed installed and never see any problems with either of them, so it sounds like something got messed up.
The only time I've seen long delays before playback, users have fiddled with cache settings to avoid buffering after following some nonsense advice and set an insanely huge cache size; which needs to populate before playback can start.
remove the Options= ?
Run "getedid create" and then reboot. The getedid script will capture the EDID data to a file which is then used to fake the connection to the TV so the Pi thinks it's connected at startup even when it's not.
I always like to ask the question: does it work good-enough for your use-case? .. because users frequently obsess over how to force a device to use 5GHz "because it's faster" but the kernel 80211 framework is written to figure out which frequency band gives the better signal and use it, so while 5GHz theoretically is faster it's also more susceptible to poor signal problems, while "lower speed" 2.4GHz with a better signal may give you higher throughput. It's also important to focus on "fast enough" vs. "max theoretical speed" because if it *is* fast enough, it's fast enough. Only "not fast enough" is an actual problem. NB: Regdom can be set from within the LE settings add-on these days, so no need to use modprobe options files.
H264 10-bit is not a broadcast standard so almost no SoCs/GPUs support hardware decoded playback and software decoded playback is VERY taxing on the CPU. Your clip is also high (5.1) profile with 16-reference frames. Historically we see most animé fans using an Intel NUC with a fast Core i7 chip to handle such media - it also cannot hardware decode but the CPU has enough oomph. What you're describing is exactly what i'd expect from any ARM SoC including an RPi4. The only solution for playback an RPi4 would be re-encoding the file to 8-bit H264 or 10-bit HEVC, both of which can be hardware decoded.
If it still has an internet connection you can pastebin system logs from the settings add-on. Share the URL displayed on-screen and we can see if there's any clues to what's going on.
Clean reboot and demonstrate the problem, and the log will be under 512k.
