no , you are able to embed both subpatches and objects into a single patch.
click on the object/patch and the right click, and you will see an embed option.
re embedding: that's what I thought I did. (If I click on "embedd as patch/object" on my demuxer objects (not the subpatch!), the objects end up with an "edit" button, no "update", but I suppose that's normal for objects)
Anyway, I played around some more and found that I can run exactly 51 demuxers in an otherwise empty patch, but not 52. Each added demuxer adds about 580bytes to the overflows. By my calculations that means that one instance uses up around 580 bytes, and the total sram is about 30K, which in turn means that any patch that won't tolerate even eight of them uses over 25K in sram already.
Not knowing the first thing about what needs sram and what doesn't, I suppose I will just take that to be a normal sram usage and look for things like dials and displays to eliminate in the main patch.
Sorry if that was a wild goose chase, I'm learning...