replying to myself - not form scratch after all - uses chromium as the base...
From the forum re memory usage/optimization:
"Not to burst some bubbles, but I'm afraid that great optimizations will never happen.
Chromium is the base of Vivaldi, and Chromium is resource hungry, period.
Optimize Vivaldi would mean to fork and heavily patch its code base, that would be an effort impossible to sustain for a small company like Vivaldi.
Surely some small optimizations would be possible on the Vivaldi specific code, but don't expect miracles.
If you are on low end/old HW Vivaldi isn't the browser for you, better to look at Otter, Qupzilla, Fifth browser, in that case. "