Ok finally figured everything out! The first thing you need to do is go into the Retroarch GUI/Menu and go to “options” and then go to “core options”. Make sure the “Neo Game Mode” is set to “unibios”… I also set my gamepad option here to “newgen” as it seems to map the controls better but you can play around with that. You can save this config file in the main menu and copy it over to the retroarch.cfg for fbanext so you don’t have to do this every time.

After that, if you load a Neo Geo game such as Metal Slug, you can hit the Neo Geo buttons A + B + C during the rom boot up to access the full UniBios Menu. Here you can change the game region to what ever you want, and also change it from arcade to AES (console). Any changes made here will be saved until your change them again…

After you do that, exit out of the game and reload it. During the rom boot up, hit the Neo Geo buttons B + C + D this time to bring up the Test Mode screen. Here you can change all of the gameplay settings such as difficulty and BLOOD. When you save this, it again will be there even after a full system reboot so you can edit to your liking’s and not have to do it again. Hope this helps, took a while for me to figure everything out on this!