LED Landscape Lighting
I have close to 40 fixtures around the yard and draw less than 50w total, based on my Killawatt device readings. The proposed 10W transformer sounds about right.
According to my favorite supplies or LED lamps, those standard, DIY transformers may not be good for LED. They may provide too much voltage, especially at startup. They recommend a "regulated switching" power supply, presumeably because of greater voltage stability over a range of power.
LEDs, in general, are more tolerant of voltage range than incandescent, without noticable change in brightness. This, combined with lower current, makes wire length and voltage balancing less important.