Hi @Will_Springall welcome here, feel free to Introduce yourself 
if you’d like!
Editability: When loading CAD geometry intro Revit, Speckle loads it either as a DirectShape or as. FreeForm element. Neither of these are editable in Revit, and so you will have to edit them in the source app, and send them again.
Block Support: This depends a bit on how you are sending the blocks to Speckle. In Rhino and Grasshopper we provide more advanced control over how these get converted (see Rhino Mapper and the Grasshopper BIM nodes). I’m not sure what happens with AutoCAD blocks, but @clrkng should be able to confirm.