You probably mean the construction measure, i.e. the octameter step of n times 12.5 cm (-1 for walls, +1 for openings). Yes, that helps you avoid botched pockets (pointing overextended joint gaps) if you take that into account in the floor plan. With room heights and parapet heights, various things can be "balanced out" by small-format skirting or finishing layers, so you don’t have to think too strictly in stone formats there—especially not in terms of room height jumps of exactly 25 cm. For openings, window and exterior door dimensions are uncritical; especially the parapet height is often "balanced out" with sawn stones anyway. For interior doors, it is highly recommended to use standard sizes (height commonly 213 nowadays, living room doors 88.5, bathroom doors possibly also 76, storage rooms also 63.5, front doors 113 or 101). I recommend terrace doors at 113, and I would always keep window sashes under one and a half meters.