Legal regulations for eBikes

Hey everyone!

Been tinkering with my Class 2 commuter eBike (a converted hardtail MTB) lately, mostly upgrading the battery and controller for better range on my hilly commute. It got me thinking about the legal side of things, especially with DIY builds. What are the main regulations you guys keep in mind when modifying your eBikes, particularly regarding motor wattage or speed limits? I'm curious if anyone has run into issues or has tips on staying compliant while still getting the performance you want. Cheers!