I'm having the same issue. After launching the game, the menu works fine, but when I get into a match, my GPU usage spikes to 99%. After leaving the match, the GPU remains at 99% usage, and you can see even the menu lagging.
My solution is to enter and exit a match, then quit Ultimate Team mode and go back in. It might take several cycles of this. I keep an eye on the GPU usage – when it drops, it means the game has started working normally and I can play matches with smooth FPS.
This usually works until the next game restart, although sometimes the problem can recur when entering a particular match, but that has only happened to me twice.
I've seen this problem discussed often in the community ever since EA FC 26 was released, but EA, as always, doesn't seem to care. It's clearly a case of poor optimization, and it's their responsibility to fix it. After all, nothing like this happens in other games.