Its coming with a new Mac OS and different hardware adapted from the iphone / ipad. May break compatibility with some older products. Best to wait and see if there are any issues.
If your objective is fanless, its relatively straightforward to build a fanless pc as long as you can source an appropriate chassis (tougher these days due to imports being more expensive). You also get fanless pre-built PCs with low powered chips. An even cheaper option are the various raspberry pi based devices