The motorcycle's throttle holder was made of plastic, screwed in the cable fittings, and when the nuts were tightened, the metal fittings came out, so a helical insert was required.
I used # 2, but it bent and failed.
It seems that # 2 does not work if taps are set in advance.
I used # 3 from the beginning and it worked as if nothing had happened.
There seems to be various procedures on a case by case basis.
It is enough to buy one kit with inserts and nail folds and buy only the taps and inserts for the other sizes. It is considerably cheaper than buying all kits.