BIG UPDATE COMING SOON™
Yes, all those extra courses can be selected and played, with exception to the page of the Expansion Pass courses, that page is essentially just a placeholder from the creator of the cafeloader engine for the time being. Now, don't go expecting this tomorrow or anything like that. There is a lot that still needs to be done before this is in a decent state to share. Lots of things just hinge on when progress to the CTGP-CafeLoader occurs. I can work with the framework here, but I can't create the framework here lol. We're waiting on the ability to put music over the additional courses, right now they're all silent aside from the original courses, we're also waiting on the ability to put custom map objects in the game, because as things stand now, while the custom courses will play without much issue, many map objects have been altered making some of the vanilla courses to look strange or straight up crash the game. When that does become an available option, I do not look forward to the headache I'll have of having to go back over every custom course and finding which had map object changes and then altering them to be their own thing for each map that has them.
And there are other little issues here and there: lots of courses don't have maps, the changes to textures and models to in race items can't be implemented yet or the game will crash. But these are not the pressing issues that map objects especially are, or even course music. I'm sure you might have a question or two about something that might seem wrong that you might have seen in here, chances are, I'm aware of it, and there is a reason that you're seeing things the way that they are for the time being.
For now, just be patient and enjoy my older available modpack. The nice thing about the ctgp-cafeloader layout is that this will change from 6 separate modpacks to just 2, One with all the original MK8 characters, and one with the many changed characters that were available in the modpack I had dubbed Invitational. But we wont need a separate Battle modpack, as now we can separate the battle maps without affecting the race maps, and in fact have more of them as well, as things stand the battle maps total 16: the 8 from MK8 Wii U, and the 8 from MK8 Deluxe. Hopefully my next update wont be a long time, but for now when that will be is out of my hands, as I'm essentially just waiting for progress with cafeloader to occur.