First you have to test on your own if high f-stop is good or bad, my experience is not always, f8 just nice for me. Some zooms like the Zuiko 70-300mm are too soft to take moon.
High iso may be needed at 50% or less moon but above 75% is pretty bright (thus is always EV-), more zoom more bright. If there is too much color noise, just make it black/white during PP. You may need to do low grain noise reduction. Sharpening is always required. I cannot comment on the ISO for APS-C as I am using full-frame testing at iso800-iso1600 but I don't think you will to go beyond iso1600. Last time when I tested using Olympus dSLR, I don't recall using that high iso1600 at 300mm.
So you really have to try it out as I am not that knowledgeable on details.
The grain around the moon can be remove be reduce shadow but gets more visible with overexpose moon and/or sky is not clear. There are few occassion when I tried taking, it is always abit fuzzy, I read that it is may be due to atmosphere gas.
For lower zoom say 200mm, the attention will be exposure and focus as the details are less visible. Spot metering must be used.
One more thing, there is always a max zoom for "whole moon" picture where further zoom factor will not increase viewing quality at 800x600 or 640x480. Unless you crop a section for the moon surface (like long telescope) which is upsize, almost all the time is downsize the image as a whole during resizing.
Spheredome bro, I would like to ask when you use 1/125 at max zoom to freeze the movement of the moon, and at say, f/8 or f/11, it becomes almost necessary to increase the ISO.
What is your usual ISO for shooting the moon at the above setting, and are you not worried about noise for say ISO of 1600 and above?