G-Sync 180 Hz monitor

[Abiak]

I was always told that with a 144Hz monitor you should limit the FPS to 141 to make G-Sync work but now I have a 180Hz monitor, what should be the FPS cap? The monitor shows the FPS in the OSD and limiting to 177 doesn't work because sometimes it exceeds and reaches 180 FPS in the OSD, I also tried limiting to 165 and got the same result, then I tried to limit to 144 and the maximum I saw in the OSD was 171 FPS but 144 seems like an excessively low limit.
Another thing, I knew that G-Sync + V-Sync + Reflex should automatically limit the FPS but that doesn't happen, maybe it's because I'm using compatible G-Sync and it only works with true G-Sync? With my old 144Hz monitor I remember G-Sync + V-Sync + Reflex automatically limited to 138 FPS.
I read that with 180Hz it should cap automatically to 170 or 171, but since 138 and 141 are different, what should be the cap without reflex (180Hz)?