Much of this discussion replicates debate on how to secure a motorcycle. The bottom line is that mechanical security is degraded if the thief has time, and cover. There are videos on the web showing even the most expensive case hardened steel chains can be severed in minutes using bolt cutters or 24v portable grinders fitted with diamond coated cutters. Noisy, yes but if no one can hear or see...
Bolt Croppers Do It The best form of security is to have CCVT, lighting and enough mechanical security to waste the time of the thief, making it more likely they will be discovered. Then add electronic security like a tracker.
If wheels are removed fit a locking wheel nut on to one of the exposed studs so that a replacement wheel can't easily be installed.
If the trailer isn't going to be used for some time consider removing the hitch completely from the frame, but this requires good tools as you must use new locking nuts each time it is replaced.
