Depending on who you are playing or what tournament you are playing, people will set out some house rules to make the game not as gamey, or to stop the game from becoming a route.
Here are some of the example rules played with the ELO tournament:
1. No invading Russia in 1940. If France falls early, March, April, or even May. It is almost impossible for an allied player to win if the axis attack Russia in 1940. Hence, house rules for no invasion of Russia in 1940.
2. No Diplomacy toward major powers. The reason for this is simple. If the Axis put diplomacy towards the US, the US can be kept out the war into 1942 and with low mobilization, the axis win before the US even gets in the war. The axis put lots of diplomacy towards Russia and it destroys their mobilization value before Barbarossa.
Other example rules to stop Gamey stuff.
1. No alllied invasion of France at the end of 1941. 3 allied units if France at the end of 1941, with them there in beginning of 1942 will stop the Germans from building the Atlantic wall. Go figure on why on this, but it is in the game.
2. No sending the Italian fleet into the Atlantic early in the war. This is totally gamey, but done all the time. There is no way in hell the Italians could have supplied a fleet in the Atlantic, they had a hard enough time in the med.
3. No invasion of Norway by the allies after the German event to take Norway. Another totally gamey move, the allies know that the invasion of Norway will happen in April 1940 and that the German garrison and corps units are all weak except for that stupid Narvik one. Allied player takes French and British Corps, with 3 carriers and most of the French and British fleet. Attacks right after Norway event, takes Oslo or Kristianland? Axis have little to no ability to stop this. So you make it a house rule to eliminate some of the gamey part of the game.
4. You mentioned IJN shadowing allied fleets before they join the war. This is gamey, but this happens right now every day with the US Navy tracking where all the Chinese fleet is, sending subs to trail them, etc. So this one is actually not so gamey except for the supply situation. People seem to forget that Japan attacked Pearl Harbor partly out of the fact that we cut off their oil supplies. Kinda of hard to trail allied fleets without any oil.
There are other house rules that people will ask for.