ANSI and ISO are the acronyms used to describe the two most common keyboard layouts. ISO is notable for having a large Enter key and shorter Shift keys, and is more common in Europe. There's really no such thing as "standard", but yes ANSI is probably the most common, which is what your Poker will be. Your Poker is an ANSI keyboard with the Function keys, Arrows, Keypad, etc. chopped off, leaving only the main block of keys.
You will have no problem participating in group buys for Cherry MX keycaps - the base set will almost always fit.