The only real hurdle with getting Arch Linux installed is the RAID configuration. There are several alternatives with various advantages and disadvantages. The easiest is to just leave the raid enabled as per factory settings and treat the resulting partition as a single drive.

$ lsblk

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 119.2G 0 disk 
└─md126 9:126 0 238.5G 0 raid0 
 ├─md126p1 259:0 0 15.6G 0 md /
 └─md126p2 259:1 0 221.9G 0 md /home
sdb 8:16 0 119.2G 0 disk 
└─md126 9:126 0 238.5G 0 raid0 
 ├─md126p1 259:0 0 15.6G 0 md /
 └─md126p2 259:1 0 221.9G 0 md /home

As you can see the system contains two separate drives which have been used to create a single RAID partition, raid0. When preparing your storage drive during installation, you would then treat that raid0 partition as the drive to install on.

# cfdisk /dev/md126

 Disk: /dev/md126
 Size: 238.5 GiB, 256066453504 bytes, 500129792 sectors
 Label: dos, identifier: 0x000932f6

 Device Boot Start End Sectors Size Id Type
 /dev/md126p1 * 2048 32770047 32768000 15.6G 83 Linux
 /dev/md126p2 32770048 498081791 465311744 221.9G 83 Linux
>> Free space 498081792 500129791 2048000 1000M 

Alternatively, just disable the IRST and treat the two SSD drives separately.