What GPU should i get on a budget?

Hi! im pretty new to building my pc, and my GPU (RTX3060 12GB) is very much dying and i cant really play heavy games with it anymore. So ive been debating wether to get ASUS Dual GeForce RTX 5070 12 GB that is 559€ or Powercolor REAPER AMD Radeon RX 9070 16 GB that is 650€. I've heard people being dissapointed by 5070, but ive also heard that it isn't that bad, but i haven't read much about the Radeon one yet, so advice would be welcome.

Also i know this might sound stupid sorry, but how do i check if the GPU fits my motherboard?