Which other RAM types are compatible with PC2700 and maintain the same performance?

DDR266

Probably the PC2100 (DDR266) memory is hard to find now in stores but PC2700 (DDR333) memory and PC3200 (DDR400) are backward-compatible with PC2100 the number333 and400 are the clock speed of the memory and it should meet the maximum clockspeed compatibility of your motherboard as well as the processor too.

Memory is designed to be backward-compatible, so generally speaking, you can safely add faster memory to a computer that was designed to run slower memory. However, your system will operate at the speed of the slowest module or system component (the "lowest common denominator" effect). You cannot however use DDR2 as a replacement to DDR.