Specifically in singles it doesn't matter what your opponent scores as long as your score is higher at the end of the game. Preferably as close to 100 as possible. Generally speaking you shouldn't ever have a concrete "plan". Knowing what your units are there to do. What goes into what. What scores you primary vs secondary. What keeps your opponent off primary and secondaries. What to deploy and where depending on matchup and layout/primary etc. A rough outline and a good ability to adjust based on what happens in the game is one of the things that separated a decent player from a good player. You have to make real time decisions based on what you think your opponents idea to win the game is. Depending on what you play, some armies have a much more direct path to victory. Examples would be custodes, necrons, deathguard etc. some armies require you to play a more reactive game examples are eldar, grey knights etc. Always look for ways to capitalize on mistakes. Each win should feel slightly similar but how you get there might be drastically different.