To be fair I think it's the hardest position to get a good player. Even the top teams have struggled at times. Liverpool had Adrian costing them matches. Steffen for Man City didn't cover himself in glory in some matches he played. I'd say it's actually quite rare that backup keepers come in and you don't notice a huge drop off in quality.
I actually just looked at the U19 Euros lineup from 2017 and besides Ramsdale, Mount and Reece James (on the bench) it's a bit disappointing how few have had careers at the top.
Rejected more money at Palace and a move to Saudi Arabia apparently. Seems an odd move but maybe he genuinely just wants to play for a big club (in some ways) and Champions League football
Hopefully Strasbourg (who he was on loan at) are the club in for him because they've had a takeover this summer by Todd Boehly's consortium and have been spending quite a bit!
I think whether we need a new RB basically depends what job is going to be asked of them most of the time which we don't really know yet. If it's going to be a more defensive player tucked in I'm going to guess we use Konsa or Carlos there and don't sign one. However if they're expected to get forward and provide width then I'd say Cash needs some competition.