I am not 100% sure if 1000w will be sufficient since the 3090 has some power draw spikes it seems. So I would be safe and go with something just a bit more overkill.
The 3060 will run on a 1000w PSU without issues, however, the performance differences is definitely there.
I imagine a 1000w PSU will work but it wouldn't hurt to go to maybe a 1250wpsu or somewhere abouts there.
1000w will be fine, a friend of mine has a 5900x and a rtx 3090 running on a 650w psu temporarily and it ran, he now has a corsair 850w power supply and it runs fine no issues.