While Network Throttling is very useful, what about the responsiveness of your page once all resources have loaded?
You can throttle the CPU in Canary DevTools to understand how your page performs under that constraint. Timeline recordings you make with CPU throttling enabled can also better highlight (in the CPU Activity graph) where expensive operations are being performed.
If you want to try this out,
CPU throttling is the Canary DevTools experiment to enable.
Warning: This is an experimental feature currently in Canary! Things are likely to change. Some experimental features are removed.