OM is ok, but the contours are coarse and in meters. I use Gaia, which has far more capability and also works offline. But, note that Gaia has been bought recently by Outside. I’m concerned about maintaining privacy, based on the email they sent.

I should mention that Apple Maps, being vector based, can be pre-downloaded using the hotel wifi when you are in a roaming area and will work for many blocks around the hotel without using the radios. Google won’t.