Yes the cassettes are factory loaded, even the ADOX and Ilford. By my knowledge the ADOX (fotoimpex) is the cheapest at this moment: 4,75 euro or aprox. $7,32. I've used Ilford Delta 100 and I like it. Just have to give Minopan 25/100 a try. I'm also thinking about testing Copex in the near future when my Minox is back from DAG for a CLA.
There is a lot to read about 16mm and 8x11mm at submin.com. I can't speak about 16mm because I never used it. Minox is something else. I own a Minox "IIIs" a "B" and a "C". The first is the smallest, the "B" has a lightmeter and this camera I use the most, and the "C" can be used in an automatic mode. A bought all these camera's on eBay from Belgium "B", Germany "IIIs" and Canada "C" and they all where in good shape. Because most Minoxes haves spend years in a drawer the usually have to be cleaned by a specialist like Don Goldberg (DAG) I've been told Don can fix almost everything from shutter till meter. He's educated In Westlar at the Minox and Leica factory.
More about taking pictures.
Some more info.
A minox subforum at photo.net (I wish to come to apug soon)
And to get some impressions about 8x11 results:
Or my site at flickr
I hope you find your way!