Answer to: What is the maximum RAM that the 2011 21" iMac can take?I have seen this model work with 4 x 8GB = 32 GB
Answer to: replace AirPort with mSATA SSD?The AirPort card in earlier models can be replaced with other cards. I have used MPX-1132 dual sata controller successfully. I did research mSATA SSDs. If I remember correctly, some will work; they will definitely not be bootable.