I specialize in Twin Flames and soulmates and have been in union with my own Twin for a long time so I'll try to help.
In the runner / chaser phase of the journey to union, one runs while the other chases. Then the energy shifts so that the current chaser begins to run and the runner begins to take on the role of chaser. This happens so that BOTH twins can experience all aspects of the journey to union. The runner / chaser phase isn't just exclusive to twin flames, it happens in many cases of soulmates as well and it's never fun.
Twins are Yin and Yang. This means that they are complimentary. One will often possess all of the ABC traits while his partner will possess all of the XYZ traits. Total compliments. So, it's common for one to be more feelings-based and their counterpart to be more logical minded. But together, they mesh into one whole soul being allowing those traits to also mesh once the Soul Merge occurs.
I hope this helps! Blessings xo