For the second method using TWRP just create a folder called netflix in system/app or system/priv-app and put the apk inside giving first the same name as folder, give permissions 755 to the folder and 644 to the apk, clear dalvik/cache and reboot.
Thanks!
Just one clarification, not sure how to proceed as Netflix is now not a apk but a Split APK with several files in the zip. Also, there are several folders inside the zip like system\priv-app which I dont have in my phone, should I create them?. Sorry for the doubts but I have no clue..