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.