The operation of the Borderlands games was quite simple. Complete the game on a normal level and repeat there on a more difficult level for tougher opponents and more loot. Manage the game forever until you agree with another level of difficulty and repeat the process.
It's different with Borderlands 3. The introduction of switchable Mayhem solutions that specify the levels of agony of devil 3 has made things confusing. Players still wonder if the difficulty level of the second game, True Vault Hunter mode, plays a role.
There are some concrete facts about TVHM that I think they can at least verify.
1. True Vault Hunter mode allows you to explore missions with legends that are not available anywhere else at level 50.
2. In this mode, there is a higher percentage of rough and anointed enemies, which means that battles generally become more difficult and the game does not waste time if they are bombarded with enemies of the late game.
3. The way the elements work in TVHM is different from normal. Enemies are more or less vulnerable to elemental damage.
All together in one question. Is it better to generate loot on TVHM or Normal if Mayhem levels are activated?
In summary, the answer seems that there will probably be more legendary falls on TVHM, there are already more harsh enemies in the sections of the story or in the Proving Grounds or Slaughterhouse than generally better prisoners. And yet, it is unlikely that the overall drop rates improved, and if you say only boss farming, there really shouldn't be any difference between the modes.
On the contrary, the biggest differences are not the jump covers the different levels of Mayhem, where the drops of prey increase exponentially as you go up.