Follow this guide to flash SuperSU on the latest version of android wear for your watch, it should have the same OS compatibility as normal SuperSU and should work all the way upto android 7.1.1
1.Unlock the bootloader if not already unlocked
(Make sure to set up device with phone after unlocking bootloader otherwise no boot!)
adb reboot bootloader
fastboot oem unlock
2.flash TWRP for your device (REQUIRES read only access to system!
, will post working builds in post below
fastboot flash recovery recoveryname.img
3.Download SuperSU with busybox YDS included HERE
and move it to watch with adb push to /sdcard while TWRP is booted and then install as normal zip
adb push nameofzip.zip /sdcard/
4.IGNORE SYSTEM NOT INSTALLED
Boot watch to system and Now your root apps from 5.1 should work perfect. THERE WILL BE NO SUPER SU APP, IT HAS NOT BEEN PORTED TO ANDROID WEAR
squashfs is read only even with root so don't bother trying to modify system files like the build.prop.
If you would like to modify system use any Linux distro and unsquash the system then resquash it (will make guide if enough interest)
If you would like to change pixel density perform this command in either adb shell or a terminal emulator:
Please leave thanks if it helped!