Trinity Desktop Environment 14.0.3 Keeps the KDE3.5 Spirit Alive with More Fixes

I have some hardware that uses an old Intel Atom processor, so Trinity would be a good case use for things like that where 3D acceleration is not needed (and would actually slow things down).

Try Q4OS. It uses Trinity and works like a dream on a netbook

In my experience, using Compton in OpenGL mode to accelerate your desktop usually speeds up performance on low performance hardware like an old Atom processor with an Intel GPU (some have PowerVR GPUs, which generally don't work well with Linux at all) rather than slowing it down. It takes some of the burden off the CPU and puts it on the GPU. I don't think it's really the 3D acceleration that makes KDE 4+ run slow on low powered hardware.