Paste shouldn't be an issue, a little movement is usually no worries, it's the remove/replace or up/down that is worrisome, especially with the old paste, as it tends to leave air pockets/bubbles. Which aren't healthy for a cpu or its temps.
You have removable HDD trays, so if using just the bottom blue led fan, remove the tray and set any drives in the top tray. They do nothing but hinder airflow and can make any front fans next to useless for cooling, especially the gpu area.
Power = Volts x Amps. So with the cpu in Power Limit throttling, and pushing upto 70A or so, it's basically saying it could do more, but has reached a point at 107w where it's uncomfortable going any further. At 107w output, that's @ 1.5v on the cpu at 70A. That's normal under a stress test where the cpu can be expected to be pushing limits. It's a I5-9600k, that's an unlocked cpu, that's capable of more than the motherboard (B360m-A) is capable of, being locked, so the VRM's and other voltage regulatory circuitry are not designed/built to handle the kinds of power/stress regulation a Z board is.
So yes, reaching Power Limit throttling is entirely possible/plausible with that motherboard and brutal tests such as IBT or ITU.
1.5v is high, I agree with that, but without the ability to step vcore down manually, which is odd, every bios I've ever seen has the ability to 'Lower', only OC mobo's have the ability to 'Raise' past stock values. You just have to take vcore off 'Auto'.
You have to take posts/reports/videos with a grain of salt. There's going to be a high degree of variation in results. Unless you see someone using your exact cpu, on your exact motherboard, running the exact same game, with the exact same settings, same cooler, same ram, same drives etc then their temp is going to be somewhat different. My i7-3770K at somewhere around 180w currently, games at @ 55°C. Stress test at 70°C. That's at 4.6GHz. At 4.9GHz, over 200w, and my old X61 aio, I got the same results. Huge difference in capacity between your 150w rring12 and my 300w+ AIO.
So yes, it's possible ppl are gaming at 60°C, with that cooler, and even with that cpu/cooler combo, but other factors such as which mobo, vcore, LLC, OC, applied bios settings etc can and will change things, even somewhat drastically.