I’ve done some experiments there. I have 14 tags and wear 7 each at any point in time. I’ve tried using only one at a time vs 7 - and I have not noticed any difference in the effectiveness of the field in either case, the fields seem to be equally effective.
Yes, with more fields, I do sometime feels tired, but only if I am not doing my daily energy work. As long as I stick to my Shengong routine, eat healthy, sleep well, exercise - my energy body seems to handle multiple fields rather well. That said, some of the guides I work with have specifically told me not to go beyond 9 fields. I don’t plan to anytime soon, for I am already a walking decked Christmas Tree lol…
On the other hand, my GF has 3 fields, and she had to reduce them to 2 as she could not take even 3 simultaneously.
Like they say, your mileage may vary!