I have recently started using an Android tablet for GPS navigation and I am using software including OruxMaps (Android) and Mobile Atlas Creator (PC). In learning to use these several Google searches have lead me to this site but there don't seem to be many posts that specifically mention either of these. Are questions about the use of these applications on-topic?
Yes, from the links you provided they would certainly seem to be on-topic.
As you start to post here, even though I can see you have been on various SE sites for as many years as GIS SE has been in existence, I would encourage you to take our 2-minute Tour to pick up on anything that may be slightly different to your other sites.
I think What makes a good question? here is also worth a quick read.
Yes and No. Some questions might be on-topic, but anything answered by the software manual or better dealt with by the software provider's own channels (help forum, bug tracker) should be closed.
Off Topic might be: "How can I export my tracks to KML?" (manual, page 63)
On Topic might be... well, I can't think of anything because the manual is sooooo good. But maybe someone else can.