Notes app slow and draining battery

Hi all,

I have 2 iPhones:

1. iPhone SE 2020 (2nd generation) running iOS 14.2
2. iPhone SE 2016 (1st generation) running iOS 15.7.3

I know that is backwards, with the slower iPhone running a newer version of iOS, but I wanted to upgrade from 12.2 which was too old for my needs, and the only upgrade offered was 15.7.3.

I bought the 2016 iPhone very recently, as it was cheap and I like a lot of its features, especially the form factor which is similar to iPod Touch (5th gen.) which I was very happy with, and there does not appear to be any more recent iPhone of the same size -- I wonder why.

I've long been having issues with a slow and laggy Notes app on the 2020 iPhone, but it was still usable, except when I allowed its temperature to drop too much (it was cold outside) and the CPU could not run at full capacity. However, on the 2016 iPhone it runs notably slower due to the slower CPU, but whats worse is that it's draining the battery.

I've recently been having issues with a shorter battery life on the 2020 iPhone, and a reason I bought the 2016 one was to have something to use while I get the battery replaced. Now I understand it is the Notes app that is draining the battery. The draining just happens much faster on the 2016 iPhone, so it is more noticeable, and is a great problem, as I use the Notes app a lot.

I remember I did not have these issues on the iPod touch, which was running iOS 9.3.5.

What can I do to reduce the CPU usage of the Notes app? I've tried resetting the prediction data. I've also tried a "hard" reboot. I tried turning off the "predictive" option and it's still slow.

Regards,

Albert.