Sloppy modeling leads to sloppy documentation. That wall that's supposed to be 7'-0" long, but you built it 7'-0 5/64", so it dimensions at 7'-0 1/8", and the published output looks ridiculous.
Sloppy modeling doesn't clean up right in plan, section, elevation. (It looks fine in OpenGL with contours off. Great.) That means extraneous lines that either mislead the viewer or have to manually managed by you. Not everything cleans up, but everything that can, should. And sloppy modeling does not.
Once you have sloppy elements placed, you will likely refer to them to place other elements, and the slop spreads like a virus.
Sloppy modeling is not easier. This is how you model precisely:
• Use direct entry of distances. This means: Start placement, type 'R' (Hello world: Archicad default is 'D'), enter the distance and strike return.
• To place elements a set distance from a known point, move the origin (Opt+Shift) and use direct entry of X and Y by typing 'X' and 'Y'.
• If you are placing something 'roughly', it's still better to pick a number. Start the wall, e.g., and when it's 'about right', look at the R field (Distance in Tracker) and mentally round off the ugly number there. Then type 'R', enter your rounded distance, and strike return.
• Place the model with a sensible relationship to the global origin. A centerline, a corner, etc. You can reset the user origin to the global origin and 'feel around' with the cursor to see which end of Mr. 7'-0 5/64" is the bad end.
• If you're trying to center something, just center it. Draw any linear element from side to side, find the midpoint, and put something there. I would use a Center Line object because it is distinctive. Lesser but acceptable solutions include hotspots and non-printing lines. (Graphisoft wants you to use the new permanent guide lines, but I'm not a fan.) Whatever the thing, consider locking it. You can also use snap guides in AC19+ to find midpoints, or the old snap points constraint on the Control Box.
• Use a Center Point object to mark the center of curves, to make sure concentric elements are truly concentric. Show on all stories as needed. Lock it.
• Our plan-scale dimension standard is set to 1/8" precision. We only want to see output dimensions of 1/4" precision. (Unless there is an angle involved.) When you expect to see 7'-0" and see 7'-0 1/8" instead, that is your warning that something is off. Track down the 5/64" and fix it.
If any of these things is harder than clicking kinda wherever, I'm not seeing it.
Precise modeling is essential to Archicad success.