I sympathize with this poster, especially about device lag, since mobile devices seem to be slow in addition to their other problems, namely the manipulative operating systems, terrible response, bad interface, bloated and sluggish software, and lack of control over how the device operates.Many posters use mobile devices with abysmal AI autocorrect. Add to that device lag, small screens, etc and you have a recipe for disaster. So the answer, obviously, is not to post from a mobile device.
However, I can suggest a few ideas, if you must use a mobile device because you are unable to use a desk:
1. Disable autocorrect. Yep, everything is slower to type now, but it works better.
2. Use voice typing. This feature is now mostly pretty good.
3. Consider a mobile device keyboard. https://www.newegg.com/Product/ProductList.aspx?Description=mini%20bluetooth%20keyboard%20android&Submit=ENE
Good luck!