Indeed. Unfortunately, only 7600s are currently available as dual slot cards. Starts at 280€ (Germany). Then there are the Pro cards (W7500 - W7800) as single and dual slot. Start at approx. 450€. However, these are not any faster than the consumer cards.
No, you have to stay logged in. As soon as you log out or go offline, you will no longer see older posts. There are clients like Element (Matrix) that keep you online all the time.
Yesterday someone on the Talos IRC reported that he runs a RX 7600 successfully on Fedora 39. I guess, the same kernel requirements as RDNA2 (Kernel 6.1+). Not sure though.