Hi Miguel Angel,
To answer your questions:
1) Are there any cables that directly split from QSFP to 4xRJ45?.
no
2) If not, with the current equipment, are there any kind of "adapters" from SFP+ to RJ45?
We only have the below 2 that can convert QSFP to 1 GbE RJ-45
convert QSFP to SFP+ MAM1Q00A-QSA
convert - SFP+ to RJ-45 - MC3208411-T
but yet again this is only 1GbE and not 10GbE over Rj-45
3) Do we need to buy a second switch with 1 or 2 SFP+ connectors to convert the SFP+ to RJ45?
3.1) If this is the case, do you have any hint for what could be the best option to not reduce the bandwidth of interconenction between the NAS and the server?