Best practice, I would separate these two exercises by PE cycles (months), focusing on length first, using just extension exercises, such as stretching.
With that said, if you insist on doing lengthening and girth exercises (edema exercises) on the same day I would begin with lengthening exercises and once those are done for the day, then move on to girth work, such as pumping.
My experience is that the edema that comes with girth work can be counter productive during lengthening exercises. The edema can absolutely carry over, some degree, to the next day.
If you are just starting out, I would recommend exhausting gains from jelqing. This is a great exercise that incorporates both lengthening and expansion.
There was a time that I would isolate just extending Monday-Thursday and then move onto just pumping Friday-Sunday. While I knew I should just stick with the extending, I could not resist pumping on the weekends because I love sex with the immediate expansion afforded from pumping, yes, I am another victim of immediate gratification:-)
Like you said, we are all different. Definitely feel things out for your self, but there are definitely some best practice items that we can learn from others that have already done some of that trial and error for us.
Also, if your pump currently does not have a gauge, I would pick up a pump with a gauge when you have the opportunity. It’s helpful to see what your vacuum is measuring at.
May the gains be with us!