Great thanks! That's what I did too - didn't seal just replaced it directly.
Comparing the old and the new expansion plugs - of course it looks identical - but I don't feel/see any difference between them. I would've thought the old one is much harder therefore causing the leak due to low flexibility (if that makes sense). With the plastic toughening up it doesn't seal as good and therefore causing the leaks - is this the reason why it was leaking in the first place generally?
To me - they both seem to be the same level of hardness. Can't see any diff.
Right after replacing it - I was still seeing the white smoke and can smell burning oil. Could've been the old oil - so I washed it down. Afterwards, I don't notice any more burning oil thus far (knock on wood).
The replacement seals are a bit "taller" than the old ones and seem to have a gap in between the block and the end cap of the rubber insert. This probably was redesigned to prevent heat distortion from the engine block.