Hello,
thank you!
I think I´ve not installed a special driver for M.2. But it is important to switch to AHCI and UEFI in BIOS.
If you don´t switch you can not see your M.2.
I used FakeSMC.kext, GenericUSBXHCI.kext, VoodooPS2Controller.kext and IntelMausiEthernet.kext from Rehabman:
https://bitbucket.org/RehabMan/
And bootloader I´ve installed Clover_v2.3k_r3424.
It is required to replace the original config.plist installed by clover with config_HD520_530_540.plist from Rehabman:
https://github.com/RehabMan/OS-X-Clover-Laptop-Config
For touchpad I´ve copied ApplePS2Controller.kext from your archive (E7450_update.zip).
It works on my Latitude E7470 installed on intern SSD (SK hynix SC300 M.2). LAN (Intel I219) works too, but WLAN, Audio, Bluetooth doesn´t work.
No driver support for Intel Wireless-AC 8260, but it is work in progress see: https://github.com/ammulder/AppleIntelWiFiMVM