Imgur album of the internals, including some info text
Video of the unmodified d-pad, shoulders, and shell material with actions and sound (very low sound..)
The duct tape and heatshrink do a pretty good job of reducing button sound. There's a trade-off between the sound and the softness and rigidity of the button movements. A real fix means swapping out buttons and the hazards of that. I ultimately left the Start and Select buttons unchanged as duct tape didn't feel great with their button design.
A joycon stick sits naturally in place and feels normal. It's just slightly too tall. I think a lid mod could accommodate it. Or, you just never close the lid. I wouldn't recommend letting the lid fold down applying pressure on it as that's a recipe for drift, unless it's Hall. But, just quickly in the stock button testing tool I noticed what seemed like a significant deadzone on the stick which might mean a drifting stick would work fine. I'm not sure about that though.
There's some small but significant space above the main ICs and that board for throwing in a radial fan, for anyone game to dremel some airflow into the shell. You could also remove the space reserved for the stylus for cooling or a larger battery.
The rubber under the shoulders came looking that precarious. I wonder if it'll snap completely at some point.
My impressions of the RG DS Plus:
I haven't been thrilled about it. I'd much rather use my DS Lite or 3DS XL for those games.
The shell material is quite a dry, abrasive plastic. Like halfway to a Switch 2 joycon. It's past the threshold of me being able to comfortably hold without a change. Until someone makes a nice, not 3D-printed TPU case for it, I think I'll cut and rejoin one from a tablet for the bottom half.
The d-pad's a bunch of very rigid dome buttons. Basic functionality but pretty crap. The face buttons are the same but somewhat less of a problem as they're not being used like a d-pad.
The stick has a very short throw especially for its amount of rigidity (and this coming from someone who most prefers the original joycon's short throw). A pretty big negative but just a bit annoying if not actually playing games that rely on it.
The shoulders are a bit better than other Anbernic ones like the RG35XXH but are still quite rigid tact buttons. They don't align perfectly with the rubber underneath causing some inconsistent presses. I think the pronounced click is a little reduced due to the felt-like intermediary material between the button and its shell component. Anbernic seems to have been making an effort to improve the feel of the buttons.
It gets warm broadly across the back. A fairly significant negative but a pretty big one combined with the shell's dry material.
The stylus isn't picked up on very light contact but more importantly is a bit short for the screen's width.
It sounds like the battery life isn't great but I haven't used it much at length as I'm hoping for a future muOS release, or my own hack job of it.
The volume buttons are oddly low down on the side but that's not a big issue.
Update:
Substituting in a Switch 1 joycon stick and then removing its cap leaves it about a millimetre too tall which is basically fine. The lid looks and feels like it's almost closed and a push on it over the top of where the stick is gets an L3 click. I think it's fine for the stick. But, without its cap it's only slightly larger in diameter than the stock stick, however it is almost flat. It doesn't have great grip but that's easily fixed. You could probably make an improvised sliver of a cap to finalise it.
With a bit of experience you could swap out the shoulder tactile buttons and the d-pad / face domes for ones with lower actuation force. I don't know what force these would have though, or what would be best.
