iPhone not connecting full speed on wifi

Hello - I have an issue with my iPhone 12 Pro. I have 400 mb of Internet at my house. When I connect thru wifi on MacBook Pro in the same spot, 3 feet, from wifi, I get full speed. However my phone reads 100, sometimes 200… using fast.com or speed test.net via safari or app. Same thing. I nuke my phone, nuke my google routers, even reseat modem … haven’t found the issue. Any ideas?

Can you try another computer or iPad and another phone? Are you able to check in your wifi admin which bands or channels your devices are being assigned to?