As long as you are not at the current level cap and have Mayhem mode on, all enemies that you will face and loot that you may acquire should be within one level of you (under or over). In other words, the DLC's scale to your character's level and can be played anytime on Normal difficulty without Mayhem mode turned on.

Does Borderlands DLC scale with level?

All the DLCs scale depending on your level. The minimum level is 15 for all but Knoxx one, which is lvl 35 min.

Does Borderlands 3 DLC raise level cap?

Another big change coming to Borderlands 3 is a level cap increase up to level 72. ... This new update comes after Borderlands 3 has received numerous balancing updates, as well as two season passes worth of DLC content.