No way will a party tap work, unless you come up with another way of increasing the resistance. Some people have inserted epoxy mixers into the lines.
If you have two regulators, they can be set at different pressures. No problem there. I have secondaries because I found a good deal on them.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk