2021 16″ MBP M1 Max is the specs of your computer? And if your timeline is very laggy when running, its likely your specs on your computer, most likely the RAM. The question would be, how many RAMs you have on your machine. Also CPU/GPU is also a factor for Premiere Pro to do the playback well. But if anything, you can pre-render the whole timeline first and then when you play it, it should play as it should with no lags. Hope to hear back from you soon! 🙂