I have run both together. But it was npp and tren ace. 700 mg npp. 350 mg tren.(with 700-1000 prop).
Many people have deca dick issues and that's a deal breaker for most dudes. It funny you...might lose some hair,cool... Might get oily skin and acne, kuhl... Might get moon face and hold a ton of water, no problem...but you might get a 80 percent hard on, aw hell naw. I'm not prone to deca dick so that was never a problem in planning the cycle.
I mean it was a pretty good cycle. For me I really react pretty benignly to all aas but winstrol and tren. I really lose hair on winny. And on tren I get all the sides. Bp, red face, night sweats, regular sweats, acne, prostate, hair loss etc... I'm not huge on tren and typically I just run it when I'm really trying to sharpen up and even then it's soft doses. So I'm not really in the tren fan club. I would prefer an npp/deca and Masteron. Masteron gives me the hardness and strength increases like tren. Without the muscle growth or sides. Npp and test are for the gains.
But to more directly answer you question I would say if you have had deca dick before, you would likely get it with tren and deca together. I know caber or prami will help clear it up (or so I have heard).