It does not matter if you want to mix or isolate. It is true that concentrating on length exercises will sacrifice some small amount of girth gains. Based on your stats, I would think you would want more girth (if you have excess capacity).
Your girth exercises should concentrate on maximizing expansion. Contrary to the above post, it would be best for you to jelq at an erection level below 50%. This is a bit of a misnomer, we should be talking about engorgement levels, you want your penis to be fully engorged but in a flaccid or near flaccid state. In this way when pressure is applied maximum expansion can be achieved, thereby weakening your balloon to accomodate more blood.
A fully engorged penis will hang down low and be close to maximum girth. This condition is absent arousal, if you squeeze hard at the base of your penis the resulting pressure will straighten out your cock into an erector (minus arousal). PE is best done in these 100% tumescent states completely lacking the hardness that is created by arousal and the venal valves shutting down. A lot of people here mistake this condition as being their new flaccid size, it is only an engorged member, as engorgement is continued your nearly full length starts to periscope as a condition of the appendage filling with blood.
In this state of engorgement you can get at nice girth gains and an improved and larger helmet. PE exercises are best done in this limp and engorged state, there are some exercises that promote widening of the arterioles (bigger pipes) that are best done under erect states. Erect and engorged are different animals and should be differentiated in this game of “a bigger boner.” Hang long, hang tough.