Thanks for the additional info.
The whining noise is most likely generated by the capstan motor tachometer. It's a "head" that reads the teeth embedded into the motor exterior. The head is usually isolated by a rubber mount in order to reduce this whining noise. See if it's intact (the rubber mount). Also the head may be too close. Moving it slightly away may reduce the noise. It's normal for the noise to almost disappear at the lower speed. If all else fails you could just install some sound barriers around the motor area.
If you play a TP tape on a deck set for NAB play EQ, then the high-frequencies will be abnormally "hot" (louder) and the bass will be attenuated (softer than normal). You could compensate with preamp tone controls, but it would not be ideal. And yes, your NAB pre-recorded tapes will not sound correct (tonally), if you play them back with IEC EQ.
Try downloading a service manual and an owners manual to see about converting to IEC play EQ (or if there is a NAB/IEC switch). You never know, it may already be set for IEC EQ. Just playing an IEC frequency response test tape could determine that.
Tim