Yes the advice here will help and you can start making decisions about which tradeoffs to make based on the game your making.
Performance is more about level design and optimisation e.g. spawning enemies, limiting the number of polygons rendered at any point in a scene, working with segments to maximise culling, careful use of transparency and post processing effects etc. Memory is more about fitting your game within the 32bit constraints of FPSC, trying to reuse segments and assets where possible, budgeting texture sizes e.g. only using higher resolution for characters, balancing lightmapping quality and resolution etc.
When you first start using FPSC you have this idea in your head that you can design something quite detailed using lots of unique segments, textures and entities etc but unfortunately its not the case. Once you starting adding detail to a map you'll notice the memory consumption creeping up very quickly. Black ice mod helps with this by decoupling the new lightmapper from the build process but its not a silver bullet.
In all other respsects memory management in FPSC and GameGuru is a major issue. If you look at the Black Ice showcase demo, I only just got this to fit within the memory cap for a single map. The main objective of the demo was to show you can achive good performance in a full scale map set in a location which combines outdoor and indoor areas. A workaround for this would be to publish your game as individual episodes with a launcher.
The problem is as the FPSC community grew in size and talent, we kept pushing the boundaries and expecting more from the engine but the fundamental memory cap / management issues were never properly addressed so you have the promise of great looking games with lots of levels but not the reality. Also whilst this was going on other game engines started offering free versions and becoming more accessible which gave FPSC more competition from larger developers.
The memory issues will always keep FPSC from being a serious game engine and rather something to have fun with and produce cool demos etc. Personally I wouldn't even risk publishing a commercial game with FPSC as they become very unstable after playing for a while and usually crash due to lack of available memory which just isn't acceptable if your paying for something.