I don't claim to be an electrical whiz- far from it in fact

I'm going to be re-wiring my CP to make things neater, conceal wires, and make it removable. I'll be using 25-pair wire coming from the CP, and going to (1) IPac and (1) OptiPac. I'd like to wire all of the inputs on both boards, which totals 48, plus a +5V and GND, brings me to 50- using up the whole cable
I know I can chain all my grounds to a single point, but can I do that with my power lines also? How many items can I power with a single +5 feed from my power supply?
I think the term wired in parallel is the right one to describe what I'm thinking
+--------led
+5V---------+--------led
+--------spinner
WOuld this be too much of a load, ie would the leds be dimmer than using independent leads from the power supply?