I use Gold plugs on oil pans, diffs in the Toyotas because the diesels have Mag-hytecs, all transfer case drain plugs and trans drains, basically everywhere I get gets a Mag-hytec or Gold Plug It catches black metallic goo.
I absolutely believe in them. The less metallic goo and savings circulating eroding seals and causing particle streaks in bearings. As an experiment, because some also say Filter Mags are a waist because they say the oil filter would catch "that metal". I took off Filter Mags and the drain plugs had more goo, not much but noticeable. So I don't believe the filter will catch all the metal going through it, only larger pieces.
I put the oem plugs back on and slapped rhe Filter Mags back on, the inside of the can had a bit more black goo. Yes, with a good oil filter, a quality magnetic drain plug and Filter Mags ALSO help. I belive in all three.
If I had to rank most important to least, I'd say oil filter, Magnetic drain plug, then filter Mags. I run all three on everything except the 2gr-fks uses a cartridge and the 6.4.