I use easy tackling against stronger teams. Due that, usually against stronger teams we recive more yellows and the tendance is to fail more in tackling... I don't have proofs really like with all the other things ( trainings depending of condition, victories despite condition... counters... etc...)
But I use easy tackling.
Then the idea-own theory should be that hard tackling work against lower Q teams due that the Quality of our players is high and they don't fail... but as I said.... and like with all things in this game, theres no definitive "studies-proofs", just prophecies lol