I PREFER to use them all together, Especially when getting ready for a powerlifting meet. Those are the only three injectables i use but i rotate them at different times. Sometimes i'll run Test E/Deca, sometimes Test Prop/NPP, sometimes Test E/Deca/Tren Ace, and sometimes Test Prop/NPP/Tren Ace. It all depends on what i'm trying to do.
That being said i am very conservative with the amounts i use, even when using all three together i will barely break a gram of total gear. Alongside HGH and you really don't need much anyway.
I have come to notice that after being on test and deca for a while, if i add in a heavy androgen like Tren i will see really quick increase in strength but eventually it's like my body adapts and i won't see another increase in strength until i drop the Tren, then all of a sudden ill get really strong for the next 2-3 weeks after dropping it.
I seem to experience a lot of shit that doesn't necessarily fit the framework for how we generally think this stuff works. I think it's because the body is just so damn complicated and none of us our doctors but we try our best at analyzing and assessing what were experiencing.