How do I find the right iPad Series for my needs?

You would need first identify an iPad you may want, and then determine based on the iPad info, what iOS version it can run.

This one for instance: click here ➜ Apple iPad 11-inch: A16 chip, 11-inch Model, Liquid Retina Display, 128GB, Wi-Fi 6, 12MP Front/12MP Back Camera, Touch ID, All-Day Battery Life — Blue - Amazon.com

This is the most recent regular iPad released by Apple, can run the current iPadOS 18.5, and will be able to update to iPadOS 26 in the fall. Amazon has it for $50 less than Apple.

click here ➜ OS - iPadOS 26 - Apple

Also, you can reference the following support document for all iPad models and the latest iPadOS version they can run compiled and maintained by yours truly.

click here ➜ Complete List of iPads, release year and iOS version they can run - Apple Community

Yes, some amount of research will be required to determine what iPadOS version the iPads on Amazon can run.

How do I straighten this mess out?

Easy. Avoid Amazon.

In spite of their supposedly being an Apple reseller, I do not trust them. I see other Amazon "official store" sites that show too many listing that are clearly not products from the company "represented." Just recently I visited Amazon's Nikon Store and found several "bundle"l offerings that clearly had after-market lenses and accessories that Nikon would not have included.

In 20+ years I've also seen many sad stories here from people buying from non-Apple sources and getting burned.

The only discounted Apple products I trust are from Apple's Certified Refurnished page. We buy Apple refurbs all the time and none have been less than excellent. Apple refurns may not be available on all countries and regions. If they are in your area, it will be listed in the Apple links at the bottom of your Apple home page:

Another vendor trusted by many senior contributors here is Other World Computing. OWC also has very good before-the-sale support for help in understanding what to order.

try this first:iPad - Compare Models - Apple

Amazon is fine. It is an Authorized reseller and their discounts are real, really good in many cases, and the devices are fully Apple supported and can be covered by Apple Care+ if required.

Just make sure the device is being sold by Amazon directly and not some other 3rd party seller.

It's good to be weary of 3rd party sellers on Amazon, but un-bridled fear mongering of the entire story is unnecessary and uncalled for.

And, yes, I just bought an iPad from Amazon. It's an Apple product, discounted yes, but brand new in sealed box, and can be covered by Apple Care+ if I so choose. See link above.

All iPad models have broadly the same core capabilities. Models essentially differ in their ultimate performance and physical attributes. iPad Pro models use FaceID for biometric user-authentication, while others use TouchID.

You can compare iPad models here:

iPad - Compare Models - Apple

The iPad (A16) is the current entry-level iPad. The iPads Pro M4 are the opposite end of the scale - top of the range, with cutting edge capabilities and hardware. Between these two extremes are the iPads Air M3, these offering a mid-range high performance option. The iPad mini (A17 Pro) is perhaps an entirely different proposition - offering a smaller form factor and other differences in hardware and ultimate capability.

Whichever iPad model you choose, you would be well advised to purchase as much internal storage as your budget might reasonably allow - as internal storage (and other hardware) cannot be changed, upgraded or extended. The available internal storage is fixed for the entire life of the device. If you run out of internal storage for your documents, photos and other data, you will forever struggle and become a source of frustration. It is far better to have more storage than you need, than to need more storage than you have.

A good rule of thumb is to quantify how much data storage you will need - add a healthy margin - then double it. If you are unable to quantify your data storage needs, it becomes more difficult. Whilst I and others cannot make definitive recommendations for your personal needs, objectively I would council against purchase of any iPad with any less than 256GB storage, 512GB and higher having a greater margin for growth if your needs and interests expand.

Within the Apple Support Communities we see regular tales of woe and disappointment when storage requirements are exceeded, necessitating replacement of the device; by contrast, we never see complaint of having too much available storage. It is relatively easy to fill limited internal storage space; perhaps consider higher tiers of storage as providing room for growth as your needs develop or mature - potentially extending the useful usable life of the device. 

Also consider the functional differences between WiFi Only and WiFi+Cellular models of iPad. Aside from the obvious Cellular functionality, only WiFi+Cellular models include GNSS/GPS location capabilities - which may impact any Apps or features that require accurate and consistent location data, such as Mapping. 

Purchase of a WiFi+Cellular model provides access to precise location services, but does not commit you to using Cellular connections. WiFi Only models of iPad have no Cellular or GNSS/GPS functions at all.

Thanks Phil. I defer to your buying experience.