I recorded many documentary cassettes that included music during the mid-1970s, and transferred them to digital over the past ten years using a Nakamichi Dragon. While a few of the old cassettes jammed mechanically and their tape packs had to be transferred into new shells, the overall sound was still quite good, depending on the recording conditions, of course.
But just as a comment on one of the messages above, the maximum dynamic range of a Dolby-B cassette is only on the order of 60 dB, so 16-bit transfers are more than adequate (way more, in fact; 12-bit transfers would have been equally good!). Certainly nothing is gained by using 24-bit encoding with cassette source material. Even 15 ips Dolby-A master tapes (which I made plenty of back in those years) don't match the dynamic range of a 16-bit A/D converter.
Optimal azimuth adjustment definitely matters--otherwise you don't get the high-frequency response of the original recording, and then the Dolby system mistracks as well, increasing the degree of the loss. Over time all tapes lose some of their short-wavelength magnetization, which of course affects the high frequencies the most--and with slower-speed tape this effect is more pronounced, because then even the upper midrange frequencies have short magnetic wavelengths. Maybe you can rent or borrow a Dragon somewhere?
--best regards