@Gwen-Dragon
Well I've tried Vivaldi on MacOS X 10.11.6 (El Capitan) powered mid-2009 iMac and I can say that it works pretty well for 8 year old machine. Unfortunately I'm not able to test on anything older (lol that PowerPC G4 mini on 10.4.11 Tiger won't cut it).
I've already presented Vivaldi to some of my friends (clearly power users). I'll probably create a new thread with some extensive description on biggest local (I mean country-wide) Apple forum too.
edit (rant):
fsck yeah Apple, this surely made conversations more precise... Mac OS = vintage non-UNIX stuff up to 9.2.2, MacOS X 10.0 (Cheetah)-10.11.6 (El Capitan) and macOS for 10.12.6 (Sierra) onwards