Get tab suspender ext.
Also some extensions harvest RAM and like never releasing, check Opera's task manager to see what extensions are high on RAM/cpu consumption then just quickly disable and enable the fat ext. U can do that instead of restarting the browser.
GPU task also is a fat hoarder sooo sloooow to release any: kill it it will be back up in seconds but much more lightweight.
Perhaps Chromium based browsers should have tighter weight watching!? Veganize em!