I have never understood why you would need an erection in order to pump because at least in my case the vacuum makes the penis expand, not the erection. Sometimes an erection is helpful for entering the pump because it is easier to create the seal with a penis already erect.
I did edging without cumming for a long period of time, during the time of jelqing - back then I didn't have a pump. In the first week the erection can be better at times but over time it always became normal again. I think it is placebo and only appears to bring better erection when done for a short while.
But during that time I could edge seeing my pleasure level going through the roof, literally. I became extremely horny. I thought that masturbation was better than having sex. I understood that no woman could give me that pleasure. December 2016 was one of the last sessions that went like this. Later, for some reason, I couldn't go that far anymore. Before I hit these high levels of stimulation I have to cum. Somehow the start of my pumping career must have destroyed the skill. But it could be imagination. Still I can't stop pumping + I tried to reignite the extreme pleasure sessions after the summer break (where I didn't pump for 1.5 months) - still his never came back and I didn't experiment too long due to lack of patience. During that time also a shift in consciousness happened in which I lost my feeling of guilt for pornography.