Per Doug Smith's list at
http://www.w9wi.com/articles/grand_fm.htm, WTTS and WFBQ are indeed the only two FMs in Indiana operating with grandfathered facilities greater than standard class B. WTTS is slightly more super than WFBQ, but the difference (5.6 dB over standard class B for 92.3, 4.9 dB for 94.7) is insignificant, especially because grandfathered stations are only protected from interference to standard B contours these days and both WTTS and WFBQ have encroachment fairly close in.
So the question of "which FM gets out best" is an issue not only of raw power but of who has the cleanest allocation, and a few others that come to mind on that account are WSHW 99.7 in Frankfort and WAJI 95.1 in Fort Wayne. WZPL seems to do pretty well, too.
On AM, it's a combination of raw power, antenna efficiency, ground conductivity and dial position. WOWO does OK on the first three, at least. WBAA's day signal deserves some respect, too, as does WIBC's. If you count transmitter location instead of city of license, the daytime coverage champion is almost surely WIND, with its transmitter in Griffith, Indiana.
On the whole, Indiana didn't come out too well in the early battle for good low-dial AM facilities. There's little in the Hoosier State to rival the big daytime reach of a WTVN or a WILL or a WKRC.
Smallest AM coverage? There are a bunch of high-dial daytimers that come to mind - 1510 in Wabash, 1580 in South Bend, 1600 in Linton, 1570 in Auburn. I'm not sure which is the smallest of them all.