As far as the border for GBA games is concerned, it may have been because I was using the default setting for all GBA games tested, which includes the soft reset and in-game save features. The border appeared even before using soft reset for all games.
I´ve used Kingston memory, both 1GB models (Taiwan/Japan) and for most games they run the same speed. When playing games like Castlevannia and Animal Crossing I noticed load time slowdowns with the card manufactured in Taiwan. It may be different for you, but that was my experience.