Multiple considerations really:
1 - was the size of the Air too big or just right? What about weight in the hand? What happens when those hands get arthritic etc. Yes, I know. This is unrelentingly cheerful stuff 
2 - direction of travel with your vision. It’s not going to get better and by the time you’re 60 you need 60x more light than you did when you were 20 so buying cheap is great on paper but may be a false economy.
3 - Thanks to the then teenager robbing their own bank account and going on a spending spree I acquired multiple small tablets which I was able to charge, update and try with the intent of using one of them for exactly this purpose and flogging the rest. In my case, at that time, Naim app and Innuos Sense.
Tried Amazon, Kindle, Lenovo, Samsung, Chrome book etc. Yes, they spent a fair chunk of their savings. 
Came to the conclusion that you get what you pay for. Compared to an iPad Mini the screens were poor and the devices laggy. Even the ones which looked fast - Samsung and the Lenovo spring to mind - were nowhere near an iOS device. I was quite surprised by this but it was what it was. Taken in isolation and without being able to compare you’d probably get used to the lag, as we do, and give it no more thought but, when you’re able to compare, it’s pretty stark.
4 - connectivity. Again, you get what you pay for. Some devices will have rock solid wifi and some will make you want to throw them in the bin. I literally did throw one device in the bin as it was utterly useless. No names. There have been some threads on here when it was painfully obvious that Naim and the wifi was not the culprit but it never goes down well with people who perpetually think that cheap things should all be brilliant so er…
5 - developers have many skills but anticipating the many twists and turns of Android and other minority OS is not one of them. Most focus on iOS because when you’re on iOS 18 there may be lots of phones about on 16 and 17 but you don’t have 50 flavours of 18. Android? Hmm. Not so simple. Generally, and this is absolutely a sweeping generalisation, if you want the app to work well then iOS offers more likelihood of that being the case over a longer period.
I had plans to use an old iPhone. My first gen. SE is on its second battery and does sterling service as an alarm which allows me to start the day with R4 7am news without having to run down my main iPhone 12 Mini battery, which is poor enough as it is. However, I found the screen too small and the tendency of Mrs. H. to put it down in random places was incredibly annoying.
I also contemplated a Mini but when in the Apple Store it was pointed out that one of the new 16 series has barely 2mm less screen width than a Mini so if in the market for a phone as well that was probably the better option.
My iPad Pro battery was end of life and the device itself was “legacy” having lasted 7 years. I kept it on life support for 6 months but caved on retirement and bought the new Pro. That gets used for the Naim app when the errant 20 year old comes home with their Muso QB and Innuos Sense the rest of the time. Your mileage may vary.
