Is the game fully optimized at this point?

I'm a huge fan of Opus Magnum and am loving Kaizen so far after picking it up during the Summer Sale.

I briefly thought I had found a new Cost record for the Compact Camera with a ¥20M solution, since the "Top Percentile" showed ¥22M as the top score, but checking this subreddit obviously showed that the cost record is ¥18M.

This got me thinking: How many of the metrics for each level are fully optimized at this point, and is there any documentation for which levels could be pushed further?

(Side note: Why doesn't the in-game Leaderboard show the top score? I assume "Top Percentile" is showing the average of all of the scores in the top 1%, but that seems kinda silly to me and I would rather see the #1 overall score.)