While those rules are true to some extent, there is a narrow window where they apply. Too cold and the engine will waste energy on each cycle heating itself up. A cooler engine should be more det resistant allowing more ignition advance and more power.
It's generally considered that 82 is optimum for power and that may be why Renault chose the 75 thermostat as standard and if I was using my car for track days then perhaps I would have stuck with the 75 but as a daily driver my car was barely up to temp on my 10 mile drive to work and running cold brings a whole load of problems including reduced economy, bore wash from being on the cold start map too long etc
The 182 thermostat is a good compromise between power and economy however personally i would prefer the fan activated at a higher temp and ran for longer as it's only an issue when sitting in traffic.
I have mapped my own cars previously on the road and still have my wideband so might look to buy the dealer version of the Rstuner software so I can play with the maps myself although it would be purely for educational purpose as from what I gather the maps henk provides for 98 Ron fuel are very good and sort out the lean spots in the factory map that were required for emissions reasons