4.) Considering your garden layout
Let us assume they make it inside your perimeter. Once there, they will prefer to immediately find some cover, preferably at a location where they have an ideal view of the house. Here they can collect themselves and check out the place at their leisure. It is for this reason that it makes sense to change your garden layout such that there are only 1 or 2 good hiding places available, and then place sensors to detect movement at those "hot spots". Remove all other possible hiding spots like large bushes or garden features that may be used as hiding spots.
It is true that by selectively placing your outdoor security beams as explained above, you are creating some "soft" areas where an intruder can enter without detection, but remember: The intruder does not know where your outdoor security beams are located, nor are they aware when they are detected!
No freestanding house should be without basic outdoor security beam coverage.
You need to be alert today in order to be alive tomorrow!