Slackware 15: AMD or NVIDIA Video Card?

I am patiently waiting for the new Ryzen 5900X to be back in stock so I can finish up my new PC build. However I am going to carry over my NVIDIA GTX 970 into the new system until the new AMD cards come out and NVIDIA restocks their new RTX 3000 series cards. I have always had NVIDIA cards in my systems and used the proprietary drivers with no problems. But I am curious about AMD cards in Slackware, are the drivers opensource or proprietary, do you get the same amount of performance as you do in Windows? Essentially I just want your opinions and your experiences with AMD in Slackware so I can make a informed purchase in the coming months. I have always used NVIDIA because of their Linux support but would consider AMD if their drivers are as solid as NVIDIA's.

Thanks.