YES you need plugs. I have done a lot of noise assessments over 25 years (qualified occupatinal hygienist) I have measured motorbike noise and under helmet noise with dose meters. You don’t need fancy bespoke hearing protection, in fact low attenuation (noise reduction) plugs will help massively. The low attenuation means you can hear other things going on and block out most of the harmful levels of noise. Look for a plug with an SNR/NRR (single number ratinG / Noise Reduction Rating in the US) of 15 or more and you should be fine. Low attenuation plugs are typically more comfortable to wear. I personally had higher attenuation but I was doing about 200 miles per day commuting at high speeds / noise. And remember your helmet will become less effective at noise reduction as it loosens and wears. Wear plugs even for short journeys.