How to find that I am rooted with Systemless I have flashed, SUPER SU 2.79 SR1 on Oneplus 3 running OOS 4.0 (Nougat 7.0). How to find that I am rooted in systemless mode ?
I have systemless root and a few ways


The superuser su binary will not be found in  /system/xbin/, like in normal system-based root. See 
Systemless Root
On your terminal emulator enter which su , it should show the location of su binary other than /system/xbin/ ( in my case it shows in the /su/bin/su location ). You can leave a comment to show the result in your case. Thanks
In Su app settings, option to install SuperSU as system app is greyed out and the text reads that this option is not available being systemless root





Some apps which have their path hard coded to search for su in above location will fail. ES Explorer is one such app, which will not work with root privileges, though rooted - not a reliable method, since the app can be updated