Maybe this will be of help:
I have just completed building some fry tanks that have one filter to clean all four tanks. This is how it works:
Tank 1, top LH drains into tank 2, top RH through 22mm pipe, Tank 2 drains into tank 3, bottom RH through drainage built into the end wall, tank 3 drains into tank 4, bottom LH through 22mm pipe, water is then pumped through a
powerhead filter back to tank 1. Using large bore pipe ensures adequate flow through, avoiding the need for switches or pump controls. Syphons have a nasty habit of moving too much water too quickly or stopping completely if the intake comes out of the water at any time. The large bore pipe is just an overflow, not a syphon.
Your option 1 is probably the best to go for, but ask your local glass company if they could drill the hole for you.