Splitting one main low voltage power line into two
I use stranded wire for everything and I work in voltages up to 480.  Wire nuts are my main splicing technique.  Never had a problem nor had any reason to think I might.   For 3#18 blue wire nuts are ideal. 

If you are worried about voltage drop, up your wire size.  Due to the strange economics of mass produced wire, #14 is barely any more expensive than #18.  For going to individual strips I use #20 or #22 because I want delicate wires that are flexible so I don't put too much strain on the strip proper.   But I splice up to heavier stuff within a foot or two.