Al, Jeremy has answered your questions. Let me put my answers a little bit differently so you get the whole and clear picture.
I had the first version of the Tero, never really liked it, but I don’t think it had all of this capability.
It had exactly the same capability, only you were unaware of it

All Specialized Turbo e-bikes since 2019 have had the same capability, only Mission Control was the old app and Specialized App is the new one.
Importantly (and differently from Tero, which had a display on the stem) your e-bike display is named Mastermind TCU and it is located on the top tube of the frame. It allows up to 5 data screens with a plethora of information (120 data field configurations are possible).
Just ordered the bike yesterday and super excited. I need help understanding the Specialized App.
You can mount your iPhone on a good third party mount on the stem of Creo. Specialized App will allow you:
- Tuning your motor (that is, setting very precisely assistance and max motor power per an assistance level: ECO, SPORT, TURBO)
- Defining how the Range Extender battery would be used (relevant in case you buy one and the related stuff such as cables)
- Monitoring your and your e-bike performance as you are riding (the Specialized App allows a big dashboard with your and e-bike workout data)
- Providing advanced assistance mode known as Smart Control:
- Ride for a defined distance and elevation gain, still return on the e-bike battery
- Ride for a defined time, still return on the e-bike battery
- Ride at a defined basic assistance; allow the system to adjust assistance so your HR won't exceed a defined threshold
- Registering your rides and uploading them to Strava
What are the downsides of using a smartphone as the e-bike monitor and ride recorder?
- Short phone battery life
- Touchscreen sensitivity to precipitation
- Hard to operate the phone in full gloves
- Phone vulnerable to crashes.
Can I plan routes with it and my iPhone or is a computer better for that.
Specialized App is not a bike GPS computer. Any of the major bike GPS computer (Garmin Edge, Wahoo Roam or Hammerhead Karoo 3) is equipped with LEV ANT+ protocol and connect to a Specialized Turbo e-bike, including Creo 2. Any of these computers allows you extracting vital information from the e-bike (speed, distance, cadence, rider's power, e-bike battery level and range). As you can navigate with the GPS computer, it records your rides and uploads your rides to many sports tracking services
but it has no downsides of the smartphone, using a Garmin, Wahoo or Karoo is a better choice unless your rides are shorter than the phone battery life (and it never rains).
I don't want to elaborate but the ultimate bike GPS computer for Specialized Turbo e-bikes is the older Wahoo Bolt v2 or Roam v2.
Also, will the bike or Spec App show cadence and speed with iPhone and do I need to buy cadence/speed sensors for that? If so, which ones work best?
As you already know, Creo 2 has speed, cadence and power sensors as the part of the system. There is also an E-Bike sensor
Also, any info on good tires with more of a road focus would be great. Maybe smaller too. 38c? Most of my riding will be overwhelmingly asphalt.
Creo 2 is a gravel e-bike in the first place. Going with too skinny tyres -- given wide rims -- would create a wrong profile of the tyre. There are also other (geometry) considerations not to go too low with the tyre size. Specialized recommends the minimum tyre width as 40 mm, and installs Pathfinder TLR Fast Gravel Tire 700x40c, GRIPTON T2/T5 on less expensive Creos. Bear in mind that installing a more skinny tyre will require you to ask your dealer to set the proper Wheel Circumference in the e-bike firmware.
Were I you, I would enjoy riding the fantastic 47 mm tyres for at least several months before you change them. Wide tyres would provide enormous comfort to your rides (not always on perfect tarmac, eh?) Any increase in the rolling resistance would be compensated by the motor. Bear in mind, it is an e-bike not a traditional pedal bike!
Many happy miles!