No. Pedaling does not affect the top speed of these bikes. The best cheap mods under $50 are MZ65 Exhaust ($35), NGK Br6HS Spark Plug ($4), Compression head ($30), and Shorty Intake ($10). These mods will increase both the torque and top speed of the engine.

Removing the exhaust baffle does increase responsiveness and torque, but will result in blowing out your head and exhaust gasket, and actually significantly decreases RPM and top speed. It also makes it INSANELY LOUD.

As long as both brakes are cable actuated, then it is a good idea.

Also, this kit is not only in stock, but is the same as the CDH kit, except for having an upgraded ignition setup, while staying the same price. https://gomaxind.com/products/pk80-80cc-bicycle-engine-kit-g4-cylinder-8mm-mounts-and-upgraded-cdi

Exhaust: https://www.amazon.com/Niome-Exhaust-Muffler-Stroke-Engine/dp/B07RN4ZY7P/ref=sr_1_3?keywords=motorized+bike+exhaust&qid=1669662578&sr=8-3

NGK Spark Plug: https://www.amazon.com/NGK-BP6HS-Standard-Spark-Plug/dp/B000XBGT7E/ref=sr_1_4?crid=A6B6HXKWB7OK&keywords=NGK+Br6hs&qid=1669662628&sprefix=ngk+br6hs%2Caps%2C93&sr=8-4

Compression Head: https://www.amazon.com/CDHPOWER-Performance-Head-Stroke-Engine/dp/B06Y64K3GL/ref=sr_1_11?crid=1YTAFSTDJR1IV&keywords=motorized+bike+compression+head&qid=1669662663&sprefix=%2Caps%2C87&sr=8-11

Short Intake: https://www.amazon.com/Mingdun-32mm-40mm-Manifold-Connector-Motorized/dp/B08J7Z71QT/ref=sr_1_5?crid=3FRSQ18FOIUDA&keywords=motorized%2Bbike%2Bshort%2Bintake&qid=1669662702&sprefix=motorized%2Bbike%2Bshort%2B%2Caps%2C90&sr=8-5&th=1