I have similarly stupid numbers of tabs open, I've tried other browsers over time as they came to market or as major new versions come out, but nothing seems to match Opera's ability to handle them. Sometimes an updated version gets a bit crashy at launch so I skip it and stick with an older one until it's patched but been using it about forever. Currently have a shade over 200 tabs open, though admittedly only a couple of handfuls are in tab groups.
I have turned off tab/thumbnail previews but they all load live (as well as retaining their histories through restarts/crashes), and also set my plugins to load only on request (and either click the play icon, or enable all in current tab from the address bar). Mostly use it on OS X now, but been in a similar position when I've had linux or solaris as my desktop OS.