You can pre-write secondaries, if that's what you meant, but you can't submit secondaries until after you receive them, which won't happen until sometime after you submit primaries. You cannot control the timing of when schools will send you secondaries. Some will send them immediately after receiving your primary, others might wait weeks, or even months.
If you are doing what you should be doing, you won't submit primaries without knowing your score (other than to a throwaway school to get yourself verified), so waiting until September 1 (when August 14th scores will be reported) to first submit primaries is kind of pushing it, but is definitely still doable, especially this year.
The bottom line is that two weeks are not going to make or break an application one way or the other, but, at some point, two weeks on top of two weeks on top of two weeks starts to add up. That some point is probably right around mid to end of September. Remember, the absolute last date to take the test is 9/28, and those folks will definitely be very late for at least some MD schools (although probably still okay for DO), so the question is, is it better to be a full two months ahead of that, or only six weeks? Again, earlier is better than later, but taking the test before you are ready is definitely worse than waiting.
"Ideal" was in March before the shutdown! The question is, what's best now? And the answer is, the earliest date on which you can perform at the level you are targeting.