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Mourinho sees Gareth Bale as the perfect choice and with what I read it no longer a rumor Mourinho seems to be concerned about the player conditions in Wales at the Nations League.
Bale is no longer the same beast in the field of play as you said but he's gaining back his fitness and with someone like Mourinho he could be the beast he once was.
At the best case possible, he would be a good player in Tottenham but he wont be a beast anymore. Premier League is definitely not a soft field like Laliga. He spent most of his time on the bench last season while other player has been working out at their best possible effort
It obvious that the LaLiga and Premier League are played in a different criterion but if we judge the future game of Bale in Tottenham through the way Mourinho usually wants to achieve his intentions Mourinho could train him into a beast once he's fully recovered.