Unfortunately I can’t advise on difficulty levels (my grading ability seems to gear towards how difficult it is for me personally and that seems to be based on lack of vocabulary not grammar levels) but I do have a fair few games that either have both text and voice over in Japanese or just japanese voice overs though I tend to play voice over in Japanese with English text.
The ones I’ve played most recently:
Tales of Arise
Tales of Vesperia
Tales of Zestria
Tales of Berseria
Final Fantasy VII remake
Final Fantasy VII Crisis Core reunion
Final Fantasy XV
Final Fantasy type 0
Yakuza 0
Yakuza
Yakuza 2
Yakuza 3
Yakuza 4
Yakuza 5
Yakuza 6
Yakuza: like a dragon
Digimon cyber sleuth
Digimon Hackers memory
Digimon survive
Dragonstar Varnir
Dragon Quest XI
New Pokemon snap
Legend of Zelda Breath of the Wild
Persona 5 Royal
Persona 5 Strikers
Stardew Valley (text based only - no voice in game)
There are others but these have all been from English versions of the game with the ability to change the in game language.
