Welcome @smartcasa
I had many of the same questions as you when I installed InfluxDB Cloud with IOX back in Feb 2023 and was told then “We still have flux accessible via the query endpoint so Grafana flux dashboards are still compatible through this means."
So you should still be able to use your Flux queries in Grafana and have them work against the new InfluxDB Cloud with IOX. For me, I too needed the Flux query editor and Data Explorer in InfluxDB (not Grafana) to help me write Flux queries, so I am going to stay with InfluxDB OSS for now.
There is also activity in the OSS community to try to continue keeping Flux an option going forward. Last month, Paul posted this: