As of April, 2015, GeoTIFF (and JPEG and KML) versions of the Historical Topographic Map Collection are available through the TopoView application.
Not yet. Once available, these deliveries will be handled the same way as bulk deliveries for US Topo and historic maps in GeoPDF. Check this FAQ periodically for updates. 
No. US Topo maps are delivered as multi-layered GeoPDF files and are not well represented as a single layer GeoTIFF image. We are investigating companion US Topo products for users of Geographic Information System software.
No. The primary goal of the HTMC project is to preserve, as completely as possible, the set of historic topographic maps in their original form. Removing the collar would separate the map from some of its history and metadata. 
GeoPDF maps are ideal for users who simply want to view or print a map.  Free Adobe Reader software enables this basic functionality.
The GeoTIFF and GeoPDF formats are available as two separate downloads. The GeoTIFF file comes with two files 1) the TIFF Image and 2) an XML metadata file.  The GeoPDF file is a single file.  The only way to get the GeoTIFF file initially will be thro
The Historic Topographic  Map Collection concentrates on obtaining quadrangles with scales of 1:250,000 and larger; a statistical breakdown is here.
USGS Digital Raster Graphics (DRGs) were created in the period 1995-2000. They were 250 dots-per-inch scanned images of what were then the most current editions of topographic maps (approximately 58,000 maps).
GeoTIFFs preserve the original paper map’s datum and projection, just as GeoPDFs do. Learn More: USGS Digital Raster Graphics
The primary interactive download interface for historic topographic maps (both GeoTIFF and GeoPDF) is TopoView.