Older airplane engines reverse the “core” thrust in a mechanical way:
More modern ‘high bypass’ engines reverse the Fan air
What both systems have in common is that they are stowed somewhere around the 60-80kts speed range as the chances of FOD ingestion (from runway contamination) increases with lower speed and warmer (if not hot) air is directed forward and ingested in the engine which increases air intake temperature which increases pretty much all engine related temperatures.
Auto brake settings 1-2-3-4-Max work at increasing deceleration rates.
So auto brake 1 the least and Max the highest deceleration rate. Using spoilers/speedbrakes and thrust revers provides braking action so a deceleration rate which means the brakes don’t have to work as hard.
So the more “thrust reverse” you use the lesser the brakes need to work to achieve the deceleration rate required by the auto brake setting.