PlugShare is the OG app for finding chargers. Once you figure out which car you'll be getting, you can configure the app to only show you chargers compatible with that car. Orange pins are fast chargers and green pins are slow chargers. You can tap on a pin to see details of the charger and--more importantly--read reviews to determine how reliable it is (especially useful for slow chargers, which are usually privately owned by businesses that may or may not take care of them, and for non-Tesla fast chargers, which have suffered from reliability issues).

ABRP (A Better Route Planner) can be useful for road trips. That said, I just completed a 6,500-mile road trip to Yellowstone and back in my Tesla and only used ABRP a couple of times in rural Nebraska and Wyoming to triple-check if a particular route was doable while planning to use a non-Tesla charger (I have a CCS adapter), but that's mostly because the Tesla's built-in nav system is so good. I found myself using ABRP much more often when I did a road trip to rural northern California in a Kia Niro EV, because the car's range was much lower and the Kia/Hyundai software interface is utterly terrible. If you get a Polestar or a Volvo (which have a built-in Android Automotive OS, which is different than CarPlay/Android Auto), that'll be fine, but if you end up with a Kia/Hyundai or a Chevy Bolt and want to do more than just drive it around town, you might find yourself using ABRP.

Other than those two apps, the rest of the apps you might find yourself using are all related to charging networks.

ChargePoint is a good one to download, because chances are you'll run into a bunch of ChargePoint chargers on your trip, and even a fair number of free chargers installed at places like hotels and shopping centers will require the ChargePoint app to activate the charger.

If I'm driving a non-Tesla, personally, I prefer the Electrify America charging network, because they seem to be reasonably prevalent and pretty reliable compared to other options. If I'm going to be doing more than a couple of charges, I sign up for their Pass+ program for a month, which knocks the electric rate down quite a bit and pays for itself quickly. Other charging networks you might run into are EV Connect, EVgo, Shell Recharge, and Blink, but there are others out there as well (such as regional networks like ZEF Energy in Minnesota and Francis Energy in the lower Midwest), and you often won't know which one you'll need until you start looking for a charger on PlugShare. That said, if you have limited data or are planning on being in an area with limited cell coverage, pre-downloading at least those apps should get you 90% of the way there; there's nothing more annoying than needing to start a charge but waiting for a big, bloated app to download over a slow cell connection, and then you have to create and sign into an account, load a payment method, add to your balance, etc. (Some chargers have credit card readers, but a lot still don't, and even if present, you can't count on them working, unfortunately.)