Does Sidonia no Kishi's 256 frame formation have scientific advantages?
Having studied orbital dynamics and aerospace engineering, I can simplify your answer down for you. 

Let's just say 1 mech exhibits a mass of about 5 units. However, the engine can lift up to 10 units, so in a 2-mech clasp formation:

(2x10)-(2x5)=10 units

This means that they effectively double the output of their engines.
So, the thrust of a 256-unit clasp formation, and let's also include the weight of one broken mech:

(256x10)-(257x5)=1275 units

This would give them an extremely long range compared to the distance only 2 or 4 mechs could fly.

To answer your question as to how they would balance it, simply cut the engine of 1 or 2 other mechs in strategic locations

This may just sound like I'm saying they can lift more, but the point is the amount of thrust generated exceeds the thrust needed to lift all of the units' mass, thus translating to more speed and range

Hope this clears it up for ya!