No. Lubuntu is designed to use very little resources which makes it faster on slow hardware where the os is a lot of the load. If you have fast hardware, regular Ubuntu might use (making this up but the point generally stands) 2%CPU and 3G of RAM and lubuntu would use 1%CPU and 2G of RAM. That would be a much larger boost if you have a much weaker CPU and only 4G of RAM, but you likely wouldn’t notice a difference on fast hardware.
Edit: spelling
I don’t think so. I think they sort of have to branch off as lemmy gains users.