As others have said, the pandemic makes this a very wild guess. My best recommendation would be to select the park(s) that are most important to you for post race medal photos/meals as your priority for the day and then roll with whatever comes crowd wise.
Aside from the late nights, this is more or less how I've treated the parks when there for races. I do allow myself a whole lot more time sitting down or watching shows to rest my legs and try to avoid long standby lines. I usually head back to my resort for bed around 6:00 or 6:30 so I can be in bed by 8:30 or 9:00 for the race. It works for me.
I will say that it really comes down to knowing yourself. I had run 5 different multi race challenge runDisney weekends and one half marathon near the end of my trip after my normal park touring before signing up for my first Dopey. By that point I already had a tried and true strategy of enjoying the parks while also taking in a lot of shows and/or sitting on a bench for 20-30 minutes as needed. Now if this is a rare trip, then you should consider that races will likely curtail your park time especially if the marathon is one of them.
I'm a back of the pack runner and this is about my norm:
5K: in the parks by 9:30am. Because they usually don't sweep the 5K, I have more time to stop during the 5K
10K: in the parks by 10:00am.
Half: in the parks by 11:30am.
Full: in the parks by 3:00pm.