There's always a discussion about magnets and computerized machines, but the fact is that these days the electronics are protected and magnets are okay. I wouldn't vouch for the earliest computerized machines though.
I use the 1/4 inch foot, #57, with my Bernina 440QE. It didn't come with the machine, but was worth the extra money. I also move the needle position to the right one click; that seems to give me the "scant" 1/4 inch.