The WD is compatible as your system supports NVMe/PCIe SSD. No adapters are required for the M.2 drive, as I had a 5570 and required none.. Yes if you want the fastest speed then stay with NVMe. Now 512 GB is listed as maximum because that was the largest drive Dell tested with the 5570. You can however go up to and including a 2 TB SSD.
I have a inspiron 5570 and the 1 T HDD which is failing.  I don't need a huge hard drive , rather have it fast.    Is Western Digital Blue SN570 NVME compatible?  It comes in 500 and 1T but I read online here that it only accepts up to 512?  Why?  Is this true someone else said they installed a 1T.   Also since I have an HDD do I need any adapters or brackets?   I also saw Crucial (Crucial mx500 SSD) has a drive it says it is compatible running their checker but is is listed as NAND SATA and not NVME so if I understand that is slower. Any help would be helped.
Inspiron 5570 HDD replacement with SSD