Dolphin is emulating everything, the CPU AND the SPU
DIOS MIOS is only a MIOS and doesn't replace/emulate any SPU functions (which is a hardware chipset, not a software you can replace like MIOS). The hardware part is still done by the Wii itself.
Not all games have a progressive setting.
The Progressive Patch force the game to stay in 480p, even if it was designed for 576i
The games that already support 480p can have problems if you use the "Force Progressive" atop of it.
For the widescreen hack, I think you mixed the two screenshot/videos origin. There were two different hack, the old one included in dolphin which DM has, and the new one in Dolphin only.
The widescreen hack in DM is
stretching the menus/HUD (link's head is at the edge of the picture)
The new widescreen hack (not in DM yet) is
not stretching them (it's on Dolphin not DM)
I used your own links.