Here is my suggested gapping/insulated rail joiners for the electrical blocks.
View attachment 30289
Because common rail was desired, I show the gaps on the inner rail only. You could choose the outer outer rail instead.
Why 4 blocks in each loop? Because you always need an unoccuppied block for a train to move into. If you have less, one train will be constantly stopping, waiting for the other train to clear the block in front.
The normal 1st approach is to have a separate power pack attached to each loop. But this gets very ugly when a train tries to switch from one loop to the other. It's almost impossible to exactly match settings on the power packs for the train to switch from one to the other. Even if you do, when the train wheels are spanning the insulated rail joiner or gap, you have both power packs feeding the same train. The goal of block wiring is to make it possible for the same power pack to control the same train, no matter where it goes on the layout.
Unless you are just watching them run independently on separate loops, running 2 trains with 2 operators on a layout this size is going to be an exercise in block toggle flipping. This is when DCC might well be worth the $200 investment (starter system plus 2nd throttle). In DCC, the throttles talk directly to the selected decoder inside the locomotive, you don't need blocks (or need to flip block togges). Two wires from the command station to the track and decoders in your locomotives are all the wiring you need to get started.
My last comment is that I personally would find this layout as drawn quite boring quite quickly. At the least, I would add some more spurs and switching opportunities. But then my wife tells me I'm a cranky old guy too.
my thoughts, your choices