Is it possible to draw different strokes (I want different line widths) in a subpath of SVG?
I know this can be accomplished using different paths, but it is not possible to use use line-joins on different paths. I want to use a line-join round with different line width.
If it is not possible, what is the best techique to draw two connected lines with different strokes (in the picture below the lines are not connected)?

A path element only has one stroke-width property, so it’s not possible at the moment to have different stroke-width per subpath since it’s all in one element.
Feel free to explain further on how you need the connected lines join, an illustration might help.
Have a look at the tubefy examples for how to do variable-width stroking and other neat effects with svg and some scripting.