Pragmasis here too. Very robust and reassuring. Steer clear of the really thick chains as they are very heavy and inflexible to thread through bikes without causing damage or inconvenience to you. You want your set up to be easy for you to use, otherwise there will always be the temptation not to lock it every time. Much like riding carrying a helmet, the chain won’t do much good unless it is used.
As well as the metalwork itself, use location as another line of defense. If the ground anchor is hard to access, the chain is suspended above ground and swinging freely and the padlock is out of reach, it makes things doubly difficult to access with an angle grinder.
When we built the garage we sunk a ground anchor right in the corner and about 2 feet down into the concrete. Being in the corner, now that the garage is full it is really hard to get to. The chain runs across the wall and is difficult to pin down and the padlock is beefy and difficult to reach.
If you call Pragmasis, they are generally really helpful at offering advice on the most secure set up.
Coupled with strong access security, cameras, a dog, security lights, an alarm and good insurance, there isn’t much more left for me to do except pray!