I haven't used iTunes for years, it hasn't even been available since June 3, 2019 for modern Mac OS's.
Not sure how the "Download Only" procedure benefits anything; and you've already done that anyway.
If you are going to install, just do it, as Nike used to say.
If the iPad mini and your iPad Air 2 use the same cpu I suppose the numeric details make any difference; ram is ram, bits are bits, cycles are cycles. Perhaps you would end up with a tiny screen display on the Air?
Life is too short for not trying a few exciting software experiments! You already said you have a backup, if you need a re-install...