Hi Chas,
I began using xDrip & Nightscout a very long time ago & couldn't see any reason to move to the Dexcom app.
Recently I started using Sleep mode, not just overnight, but also when I'm fairly inactive e.g. working on my computer. It works well for me.
My breakfast is usually one a slice of toast. Interestingly I have forgotten to bolus a couple of times & Control IQ kept me in single figures....just.
I bolus early for main meals - 30 minutes or more, & I don't low carb by any means.
Over the years I have been in the habit of walking after eating, if practical, which has worked well to reduce spikes. It is trickier with CIQ though as it may react to the rise & I can then end up dropping steeply. Exercise mode seems over the top for 30 to 40 minute walks.
I'm now doing better using extended boluses for ordinary meals if I'm walking, not just for pizza & high fat foods.
I still struggle with heavier physical exercise or longer walks, partly because I think it needs to be turned on an hour or two before starting & I'm not organised enough to do that!