yes some artic 5 paste does help or even better use extractor fan hole saw hole top case and plenty smaller holes under the case 20 holes and use one of these
https://www.youtube.com/watch?v=Q_4SW7b7P30 to extract the hot air.
don't place the pi on top set top boxes or amplifiers
fans rated at 12v but will run at 5v make sure it extracting air not blowing down onto soc
heat sinks work but like progets said 99% of them are gimmicks for rpi from ebay or amazon look at rs components for decent one and the thermal is poor so maybe combination might further help
I don't think you will do damage to the pi as these soc's have throttle architecture and will lower cpu down to 1 core min but you will experience game play issues due to this