So I see on many guides it talks about having a builder clear a tile before you build a wonder or district on it with a builder. So my question is how to plan these builders. If I build a builder just in normal gameplay usually I'm using all those charges immediately to improve tiles if not in the city it spawned it but a neighboring city. If I save a builder for clearing a tile, aren't I losing the increased production during the save period that I would have had if I used that charge on an improvement. Doesn't that diminish the value of the harvest? Is it the best practice to try to time a builder to be produced one or two turns before you plan to build a new district/wonder (to account for travel time)? Thanks for any advice.
You are not thinking big enough

you seem to be saying "but I don't always have a builder at hand" and "I'd rather spend the charge on an improvement IF I do have a builder."
Let's analyze that for a moment. At any stage other than the very early game, you should always have builders around. If not, you are doing something wrong. City tile improvements need to be added as the city grows, so except for the very early game, several builder should always be reasonably close by. Besides, some planning is certainly possible, not everything happens right this turn, so you can plan the arrival of a builder by thinking ahead.
Another argument: let's say you do not have a builder, but you plan to build a wonder. In this case, except again for maybe the very early game where harvests have little value (it grows over time with techs unlocked I believe), you should FIRST build a builder, who can then harvest, and THEN place the wonder. You have lost nothing, because you gain back the production you spent on the worker through the harvest (more or less). In addition, you now have a worker with some more charges that you can use to improve your tiles or harvest more to speed up the wonder
Your other argument is: you lose the added production of an improved tile. That is certainly true, but a harvest will correspond to many, many turns of working usually +1 hammer on some random tile. Production now is better than production over time, especially true of marginal yield increases.