Have you used a g5a? Because the g5a and the Switch are completely different devices. G5a was very ergonomic and had great analogs and better shoulder buttons in comparison to XD. Also, it has clickable analogs rather than separate l3 and r3 buttons. DPAD was pretty bad though and should have been improved. I don't have a problem with XD design either, I like clamshell too, so no problems if they have decided to do another clamshell. Anyhow, GPD seems to have taken a different route for XD 2, so no clamshell, just sliding controls like PSP Go which I don't know how good will be. It needs to be very well built or can be a disaster.
Dolphin works quite well in the GPD win because of dx12 video backend and Ishiruka builds, if not would be unplayable. In Android it needs Vulkan to get good speeds and is less accurate than windows version, because only two people work in the Android version, It needs something like a snapdragon 835 or tegra x1 to run decently for GC games, most wii games are still slow. So considering that XD 2 will use a MTK chipset, forget about dolphin, because it won't be playable, except maybe a couple of games non too demanding. In GPD WIN takes advantage of windows and dx12 backend, but not all GC titles are fullspeed (F-Zero to say just one), and many wii titles are slow too in GPD WIN. I am not a fan of ninty games or GC/WII titles except fire emblem saga, so I don't use Dolphin too much in GPD WIN anyway.
The current XD runs Dreamcast very well in terms of speed, reicast is not too demanding. Itas has video glitches but are not XD exclusive. Reicast is quiye abandonned and needs a lot of work anyway. PPSSPP runs very good except a few titles, but easily 75 percent of games run fullspeed in current XD (with 1,8 ghz firmware and some tweaking). In fact my shield tablet which is more powerful runs pretty much the same PPSSPP titles. PPSSPP is also not fullspeed in all titles in GPD WIN by the way, in spite of the fact that windows version is more optimized than android version.