I heard the reason you won't see a lot of what you hope to is that the bigger bands get very full very fast.
Its probably better phrased as "expect to miss a couple of bands you wanted to see due to lines / venue fullness / whatever". But unless you're being dumb about your schedule and showing up right when the band is supposed to go on you probably won't have very many issues.
8 seconds and The Venue generally don't fill all the way up. If you show up late you might get stuck in line (this happened to me with Menzingers last year because I tried to have it all and catch part of Mixtapes as well). For the headliners, they'll get pretty full so maybe if you like, try to show up for ALL right before they start playing you won't have room, but they are big venues with lots of space.
The smaller venues can be slightly harder to get into but I haven't missed a show yet. Show up 20 mins before and you probably won't have an issue. Biggest issue tends to be at the start of the day when the bigger venues haven't opened up so there are less shows going on. Can be a problem getting into venues then due less competition. Sometimes the really small venues can fill up for a great band later in the day too, so if you do really want to see someone show up a band or two sooner or just realize that if you miss one band, there is another good band playing next door.