I know that Wolf3D on the SNES uses Mode 7. Not for the walls or sprites, but for the entire screen. The graphics are rendered into a background tiles with a resolution of like 175x100 or something, then scaled up with Mode7 to fill the 224x192 screen. (those aren't the exact numbers, but you get the idea)
The "mosaic trick" is a way to perform horizontal pixel doubling in hardware rather than software. And to do this trick, you turn on the SNES's Mosaic feature, scroll 1 pixel to the left every other scanline, and scroll upward one pixel after each two scanlines have been drawn.
Normally the SNES mosaic feature just the top-left pixel of a 2x2 square into that entire square. But the trick makes a different set of pixels get doubled horizontally on the next scanline.
It requires a different arrangement of pixels than the normal way of drawing tiles. A tile containing these pixels:
01234567
becomes this when viewed on two scanlines:
00224466
11335577
Actually performing these scroll writes does not require any CPU intervention because you use the SNES's HDMA feature to do those scroll writes.
