For whatever reason I decided to test a bunch of games with Spiik today to see what would happen. I have a US system and I'm trying to learn Japanese, so I tested both American and Japanese games to see what would happen.
TL;DR Of the games I tested with Spiik, Pikmin 3, Donkey Kong Country Tropical Freeze, Fast Racing Neo and Twilight Princess were the only ones that will respond to your language settings without issue.
Red = crash
Orange = game has issues
Black = game doesn't change at all with Spiik enabled
Green = Spiik changes language successfully
Blue = Spiik changes languages successfully on games that default to your console language (ex. My JP copy of Pikmin 3 turns to English on my US system without Spiik enabled)
JP Game -> Region JP, Lang JP
Star Fox Zero -> Same as without spiik - text is in japanese, VO for intro is in english, all other voices are silent. Without spiik the japanese voices will play in stages for ~1/2 a second before cutting off, but don't play at all with spiik enabled.
Star Fox Guard -> voices in game cut off like in SF Zero without spiik, Japanese text
Twilight Princess HD -> all in Japanese
Pikmin 3 -> all in Japanese (intro voice over is in English because there is no Japanese VO)
Splatoon -> gets caught in boot loop
JP Game -> Region JP, Lang US
Splatoon -> stuck in boot loop
JP Game -> Region US, Lang JP
Splatoon -> runs normally in Japanese
US Game -> Region JP, Lang JP
WWHD -> stays in English
Fast Racing NEO -> turns to Japanese
botw -> text stays in english
Saanic Bum -> text actually in japanese, but voices silent
Mario Kart 8 -> gets caught in boot loop
DKC Tropical Freeze -> runs fine in Japanese
Smash Bros -> black screen after intro screen fades
Sonic Lost World*** -> still in english, but the warning message on the gamepad after the boot sequence is in Japanese for some reason ‾\_(ツ)_/‾ (not sure if this was true when testing Region US, Lang JP)
Xenoblade X -> game runs normally in English
Mario 3D World -> stuck in boot loop... and the background music doesn't loop properly for some reason
US Game -> Region US, Lang JP
Sonic Boom -> plays normally in English
Mario Kart 8 -> plays normally in English
Pikmin 3 -> switches to Japanese
Xenoblade X -> plays normally in english
Mario 3D World -> plays normally in english
Smash Bros. -> plays normally in english
Sonic Lost World -> plays normally in english
ZombiU -> plays normally in english