Usually the best locks are +16mm chains and +16mm U-bolts. I have Xena XC14- 5 foot chain and two Xena 18mm XSU-310 U Bar locks, 2 OnGuard 8024 Rottweiler, and 12 foot cable lock with onGurad 8000 series beast padlock. At those thicknesses of +16mm, you will need a grinder to cut free if the locking mechanisms is solid. Might want to add some type of bluetooth, wifi, or cellular monitor system to alert you and give you time to get to your bike or help track it down. Double-check on homeowners/renter insurance, I'm covered with my USAA home policy, home or away, $500 per incident.
I don't use all these locks at the same time. I pick what best works for the particular area I'm in at the time. I usually don't take any locks with me when I work commute because I'm riding from my garage to work and storing/charging my Rover in a server room next to my office (only I have the key). I break out the increasing layers of locks if I mount on a bike rack and need to make stops along the way. I break out the chain and U-bolts if I need to stay overnight at a hotel out of town and I can't take the ebikes inside.
Whatever security locks you pick, check out youtube videos and read reviews on how to defeat them to determine if they are worth the risk. I couldn't find a lot of videos/reviews on issues with Xena locks/chains compared to the bike specific ones like OnGuard or Kryptonite. The 18mm Xena U-bolt must be cut twice because the U-bolt does not swivel in the lock like some cheaper U-Bolts.
