Toyotas run low around 82 deg thermostat, and this is what I have in my 1ggte. I switch in the fans at 87 deg, but can't remember what temp it cuts out. If you want to keep you head gasket intact please do not have the fan come in at 10-12 deg above the planned running temp. of the engine.
Be careful with advise that you receive as often it is opinion - I received similar advice and it cost me an engine as I used a thermo switch for the fan that bought it in at 92 deg.
To be sure check with your local Toyota dealer and confirm the position with the Lexus 200.