OK, let's look at your loop-to-loop operations first. If you plan to run 2 trains in opposite directions on the loop-to-loop, one (Train B) will have to be parked at the siding before the second train (Train A) leaves the lower loop. However, once Train A clears the lower loop and siding, Train B can only enter the lower loop and will then have to wait for Train A to traverse the entire upper loop and make it safely back to the same siding that Train B cleared earlier. Not really good for rail-fanning and definitely very little operational interest.
Now, let's say that you also planned a third train (Train C) to run on the "branch." Eventually, that train also shares some space on the loop-to-loop portion of the layout and will also have to take the siding where one other train must also spend some time in the earlier scenario. Depending on the direction of travel for Train C, it will have to follow one of the other 2 trains toward their respective loops before heading back into the branch track.
To add some interest, you could also change the direction of Train C by allowing it to follow one of the other trains through a loop (assumes loops are big enough and trains are short enough), but that will require some very careful throttle control. So, I guess what I'm saying is that unless you limit yourself to running one train at a time, operation may be either boring or nerve-wracking.
I further assume that the two hidden tracks at the bottom represent staging and/or interchange. You also have two other locations (upper left and upper right) that look like they might be industry and/or operating accessory locations. If you seek operations, this just will not be enough, and if you only plan to rail-fan, why bother to put these in at all.
Finally given the dimensions of your plan, you will either need to build a couple of access hatches where the two reverse loops cross over each other or you will need to build bench work that you are willing to crawl on to reach problems (derailments, scenery issues, etc.). With 13' x 24' available to you, I strongly recommend that you search the web for track plans that will make better use of your space, but only after you decide what you are really looking for in a layout. If "watching them run" is most important to you, try double tracking the entire loop-to-loop (including the loops) part, and if you still want the branch with some operations, put a couple of passing sidings on it, too, if you don't feel like double-tracking that as well.