Sorry to hear that mate.
Unfortunately i have the exact same issues that you explained here.
I just contact ASUS support (3-4 days ago) and they are not aware of any problems with fans and myASUS software , so i guess you have to live with it.
There is a couple of ASUS stuff that can mess with fans, so you can try a really fresh windows 10 install without any ASUS software.
BIOS also plays an important role in fan speeds, you can try to downgrade it.
There are some reports from people with Zephyrus G14 and with the pulsing fans ('silent-loud'' in intervals) that putting it on sleep mode and waking it helps making it stop but i haven't tried that workaround yet.
Some feedback here about the pulsing fans.
I was able to replicate the "Zephyrus G14" workaround putting back on sleep and wake immediately for at least three times.
Every time fans went back to normal after coming from sleep but, eventually after some 2-3 minutes it started pulsing again.
The third time it didn't went to normal immediately after sleep, it took 10-20 secs but like i said it started pulsing again after a while. For some reason it abruptly stopped pulsing and stay normal during use.
Important to say that during the pulsing both cpu and gpu were at minimum load, temperatures were stable and only oscillated in decimals.
This is a Windows 10 install with ASUS software, windows updates done and only couple of games for testing purposes.
I believe Asus might rule out as a fan or thermal fault but i think this is a different issue.
Since the fan controllers are proprietary i can't debug more but for more tech savvy people i suggest to 'play' with 'ASUS System Control Interface' driver (as far as i know has ACPI for fan control) and MyASUS (as someone said in previous posts it also has fan control but it is hidden for our model).
This very likely needs some investigation from ASUS, so if someone can reach the correct department will be nice.
That's great progress! Unfortunately that didn't work for me, but I'm glad people haven't given up on reaching out to ASUS so that they can finally admit that the models are defective.
As for me, after sending the laptop in for repair under warranty due to the loud CPU fan a few years ago, I'm gonna send it in out of warranty hoping they can replace the GPU fan. It's just so bothersome, even if they're able to fix the problem it'll be almost 2 months without a laptop since I bought it. If I didn't have another one laying around and was dependent on this one for work I'd be completely screwed. It's ridiculous really.
UPDATE: Well, after sending the laptop for repair, and after a long wait, I was told that there was nothing they could do since they could not order a motherboard for this model, which they identified as the problem causing the GPU fan to spin at max. I'm incredibly frustrated since I thought they would fix this once and for all, but their solution, apparently, was to replace the motherboard, which I find quite odd, since when the laptop was under warranty they did the exact same thing when the other fan (CPU) was spinning like crazy. I don't know if they couldn't get a motherboard because the laptop is more than 2 years old, or if they couldn't be arsed to do so. Either way, here I am, back to square one.
At this point, I'm thinking of grabbing a screwdriver and just remove the damn fan...
UDAPTE 2: Bought a new GPU fan and replaced it and haven't had fan noise issues since. I personally suspect the fan wires weren't properly connected, but it's a new fan, maybe those fan connectors were faulty in the first place.