If you enable use of RAID via the RAID BIOS (referred to properly as an Option ROM), then yes, you will lose all data on whatever drive you set up to use the RAID configuration (the metadata written to the drive via the Option ROM will cause you to lose all data), even if you set the disks up to be considered JBOD in the Option ROM. So, if you want to retain your data, DO NOT go into the Option ROM and set up
It sounds like what you're complaining about is the actual Option ROM screen and how you want to turn it off to speed up boot time after POST. In that case, you can go into your PC BIOS and change the SATA controller from "RAID" mode to "AHCI" mode. You will almost certainly still see an Option ROM screen during POST, but all it should do is probe the disks. This takes about 3-8 seconds, and there's no way around it other than disabling AHCI mode.
I discuss the different "modes" of SATA controller operation here: