Start with this thread on MP:
Maxpass/Fastpass: an overview and some strategy.
Security changed in 2017. Now you go through bag check/security at the Harbor entrance to the esplanade, at the M&F parking structure before boarding the trams, at the DTD parking lot before entering DTD (between what used to be Rainforest Cafe and ESPN Zone -- both now empty), and by the DLH before entering DTD (between EOS and what used to be ESPN Zone). There is another bag check/security entrance for guests entering DTD from the GCH (by the Sephora store) and a small bag check/security for guests entering DCA from the GCH. Once you enter the secure zone, you no longer have to go through bag check again as long as you stay within the secure zone. So you can park hop and visit DTD all day long without going through bag check a second time as long as you don't exit the secure zone. Once you exit that zone, though, you'll have to go through bag check again to re-enter. So, for example, if you go through security in the morning, spend a few hours in the parks, then leave to go back to your hotel for a break, then want to return to the parks, you'll have to go through bag check again. Make sense?
Crowd patterns have changed since the 60th. The parks are consistently more crowded now, with (many) fewer predictably low crowd times. Mondays have become busy days. Weekends can be pretty good. Morning hours are still your best bet for getting a lot done.
Download the free
Disneyland app before your trip to start getting used to using it. MP and Mobile Ordering use the app, your TS reservations will show up on the app, etc. The app is not the same as
MDE nor are the two connected, so it helps to get used to DLR's app before you start your trip. Free wifi in the parks isn't great, so have your data needs organized before your trip, especially if you will be getting MP. Battery back up for your phone is important, too.
I'm sure other DISers can get you up to date on other changes. Ask if you have any questions!