In my experience, iOS only misses keys during the time the keyboard is loading (which can be over a second- crazy!)
But I often have input lags where I will press several keys, and then a period of time (which can be multiple seconds) will pass before my taps are registered.
The 14 Pro Max launched less than four years ago, and should not be slower than an Android which launched a decade prior.
I never had any lag on my 4yo iPhone SE until the forced upgrade to iOS 26. Now I finally understand what all those Android users complain about.