Im no aerodynamics expert but as i understand it you want the axis of the plane all around the thrust line for best IMAC style aerobatic performance. In theory you want the aircraft to fly in a dead straight line hands off (no wind). With a low or high wing the lift is off-axis of the thrust line so there will be corrections required. Vertical stab and rudder size and shape are also critical to how it behaves in yaw, especially when rudder is applied. It is possible to perfect the vertical stab and rudder so that no mising is required in KE for eg (like alot of pattern planes). You also want something that stalls gracefully and tolerates high alpha flight (for 3d etc) for this you need a double tapered wing (ie not a straight LE like an Edge! My H9 edge could be provoked into tip stalling quite aggressively) and a very light model. Conversely to gliders and jets you also want something that has a fair amount of drag so that when the throttle is shut it slows down dramatically, especially in downlines, a big prop, lots of frontal area and a fairly hefty lift section (though symetrical ofc) help.

Bearing all this in mind in theory (and i have heard supporting accounts) the Extra 260 and Yak 54 scale well down to models that behave relatively neutrally and precisely when control inputs are applied. I have neither so I cant say if this actually works out. Although I have just bought a comp-arf Extra 260 42% so ill soon find out...