Yes, you can configure all those readers to default to any font, size, margins, spacing, whatever.
The default reader for each file type (as well as whatever alternates you choose) is set in the extensions.cfg file. Then you can long-press the center button to choose which reader to open the book with. If you previously opened it, it will remember which reader you used for that file. For details, check here:
https://www.mobileread.com/forums/showthread.php?t=67149
For DRM-encumbered files your only choice is adobeviewer and that one is more limited.