I'm also very interested in MiSTer, and have been following along with the developments since I heard about it from Yodd late last year. Look up videos from a guy called Smokemonster on YT. He goes into depth on the latest developments and shows demos.
I have all the real systems that I want with everdrives, so I'm primarily interested in the arcade cores available for the system. There are a few, and even fewer that are interesting to me available right now.
From what I've learned from hanging out with some of the devs working on cores (I have a small project in the works too) the current goal is to get cores working - not necessarily to recreate the original hardware in the FPGA to the spec of a preservationist. eg. they are working to get "signal level accuracy" rather than "silicon level accuracy" which is a shame. As the work will eventually have to be done again to make it absolutely perfect. Furrtek, the guy making the Neo Geo core is attempting to make it silicon level accuracy, but that takes time and money. Support him if you can!