Hey!
So I waited on replying to this thread to see the announcements from WWDC 
It looks like even though OpenGL is depreciated, it is still going to be around for the next iteration of the macOS, and even supported on the new ARM machines. This means that hopefully we’ll be able to continue to support Quartz Composer at least for another 1-2 years; fingers crossed that we don’t run into any oddities as we transition to Metal. We’ve installed the latest private OS beta on a machine and QC support will be part of our testing.
To answer this particular question, video effects listed in VDMX without file extensions are CoreImage; these likely aren’t going anywhere, even as we transition the rendering engine to Metal.
And yep, the default blend modes will be Metal equivalents in the future, and hopefully we’ll be able to make this seamless for everyone when this transition happens.
I’ll also note that Vuo 2.0 is quite an improvement over the original. If you are a fan of QC, it is worth giving that a try, though of course you’ve got the same concerns about OpenGL disappearing at some point down the road, at least there is a development team behind the product.