This will be my 6th Expo, can't wait. I was just reading thru some posts here. My 2 cents. I have been doing the overnight lines since they moved them indoors, to get onto floor early, to get into the big panels, and avoid a long line outside (sometimes it is HOT), and I need a restroom nearby. Getting inside early also was helpful to get into the line for Stage Pass or Store Pass (I rarely get those because I am in a panel at the release time). I usually go to the larger panels, like Studios, Animation, Parks and small/medium panels too. I do not shop much, but try to get into the stores at some point. i walk the floor but it is so crowded I prefer being in a panel or on a line for a panel, lol.
The Saturday morning Hall D23 one will be the hardest one to get into. Parks is not AS popular as Studios. But still popular of course. And this time the "Studios" was split and Saturday will be Marvel and Star Wars, and I think will include
Disney+ from those Studios. (They moved Disney live action to be included in the Friday afternoon one it looks like). Many of those Sat morning people don't care about the parks, they are more the same people who go to Comic Con in SD. So they are line vets, and have no problem waiting overnight. Many people skip parks presentation because most are from CA and the Parks presentations usually spend little time on DL, and sometimes LOTS of times on the parks in China, or WDW. (going by what people have told me). This year, maybe something on a NEW Tomorrowland at DL though.
With the exception of Saturday morning, I have had luck with last minute standby lines, for small and medium ones.
I personally do not go to parks on the 3 Expo days because,once I started doing those overnight lines, I needed to grab a shower and some sleep. But some people do the Expo differently, just walk the floor, no panels, or mostly shop. Some leave in the early afternoon. Food is a challenge at Expo. They have added Food Trucks but I usually have no time to go to those. I bring water, and have brought in the small packets of peanut butter on crackers, worst case they toss them, but never have yet.
And LASTLY, the Cosplay is just one of the best things to see and I love seeing the costumes. It is so fun.