Hi, I'm not a pro, but i've been mining for about 1 year now. So from what I know;
I'd either take 3x 1200w or a 4th 1000w, because in my opinion 3x 1000w is a little too tight for 16 gpus.
To connect the gpus to your mobo you need risers (
https://www.amazon.ca/Ubit-12-PCS-Bitcoin-Litecoin-ETH-Powered-Adapter/dp/B072XGDWB3/ref=pd_lpo_vtph_147_bs_t_1?_encoding=UTF8&psc=1&refRID=FFN7KP0E3XJYBH8X5NJR)
Finally I'd divide your GPUs equally on each PSU.
Once again, I'm not a pro, but this is what I would do.
Merry Mining, and a Happy Crypto !