They are probably much of a muchness, so buy the smallest quantity you can where you usually shop and try it out.
I add butter, salt and pepper when I mix the powder up, but that is a matter of taste.
Take a look in the freezers in your supermarket. I don't know what are sold in the UK, but where I am we can buy chips that have been pre-fried and can be done in the oven in 20 minutes, pommes frittes, fried potatoes etc. And you can get small peeled boiled potatoes sold in jars in salt and water on the open shelves.
These taste best sliced and fried and of course you need a gadget that can open the jar for you, if you don't have anyone to do so.
Another idea that might be worth considering: you used to be able to buy a potato-peeling machine - they did not do a spectacularly good job, and the one my mother had back in the '60s was operated by turning a handle by hand, but if they still exist, I imagine you can get one that runs on electricity or a battery these days.
If you have anyone who could give you a hand in the kitchen occasionally and room in your freezer, then cooking a big pot of potatoes, mashing them and freezing them in foil forms or dishes of a suitable size of portion is a possibility.
Take the portion you need out of the freezer early in the day, so it de-freezes than give it 15 to twenty minutes in the oven, or half an hour with the dish placed in a collandar on whichever saucepan you are boiling the rest of your meal in will warm them nicely.
I don't have an air-fryer or any experience with them, but you can probably warm them in one , and you certainly can either use a micro-wave, or place the dish (if it is fireproof) on top of the wood-burner, if you have one and it is lit.
