Reply to upgrading firmware questions?

Hey all, im planning to buy a vci but i really want to get a good one and upgrade to the latest firmware (1.4 i believe it is). But i have a bunch of questions that i asked a month or so ago in this thread

For instace, can the VCI-100 MKII or the VCI-300/300MKII be upgraded the same way and will it function the same way, or am i better off just getting a basic VCI-100 and upgrading it for simpliciities (and moneys) sake.

also in the video is says not to use usb to serial, it says use serial to serial instead. where do i plut the serial port into my computer and where do i plug it into the vci?

Can you guys please help a complete noob trying to get into mixing with Vestax VCI controllers?

thanks!