Thanks @danj for the advice. Here is the link for my questions: Storage Solution (Speed + Storage) all inside iMac 27" 5K (late 2015)

@danj I already bought an used iMac 27 5K Late 2015 A1419 3.2Ghz. The screen is already broken, the first owner did a normal SSD upgrade (the iMac originally came with 1TB HDD) and damage the screen in the process. That's why I want to know what blade model is compatible, because the iMac does not have any Blade. (do you know if the mother board has the blade conector?) I'll replace the screen and want to do the storage upgrade after remove the broken LCD. I would like to have SSD 256 or 512 and a 4TB hard drive. Just my Photos library has 1.2TB, Lightroom 1TB, Final Cut 1TB so this library's and my personal files will be stored in the HDD, and the O.S., programs (Final Cut, Pages, Photoshop, etc..) will be stored in the SSD for performance. I already have this configuration on an 2011 iMac 27” and worked great for me. I personally don't like external devices because of my desktop space, so if you have another suggestion I'll appreciate. I also have a QNAP TS453A for Plex, backup and others files. Thanks.

Thanks @danj for the reply. And what types of PCIe blade does the iMac 27 5K Late 2015 A1419 3.2Ghz  supports?

Hi! I've been using an iMac 27 mid 2011 with 2 drivers. I upgraded the original HDD for a new 4TB HD and add an SSD as primary drive. With this configuration I have installed the O.S. on the SSD and the large files (photos, videos, etc…) is stored in the hard drive. I love this configuration because I have speed and great storage space without external devices. I decided to upgrade to an iMac 27 5K Late 2015 A1419 3.2Ghz and I want a similar solution, SSD for the O.S. and a large HDD for files, everything inside the iMac. I saw in this post that is possible to keep both devices inside, but there is a way to use them at the same time? Apparently there is no conector on the logic board for a second drive, but there is any way to make this happen, like an adapter for the logic board fusion drive conector? My iMac came with a 1tb Hard Drive (NO FUSION DRIVE). Can I upgrade this hard drive for a 4TB and buy a SSD similar as Apple uses as Fusion drive and install it? 256 or 500gb will work fine for me. Thanks!