I've come across something that would address one of your questions a bit further. The issue of flicker with TFT displays on Arduino seems to be a rather common thing, but as I was digging around, I found that there are some third party TFT libraries available which will allow text to be changed and not have the flicker effect. I guess they are able to update the screen quicker. But apparently, not al TFT displays can use different libraries. Mine is an ELEGOO TFT, and it seems to only want to work with the supplied library.