All the above is true. Also, digital recorders and computers have very little (I mean very little!) for speed fluctuations, so using an analog tape machine with SMPTE stipped on the tape could prove to be hard to do unless the tape machines tape transport is EXTREMELY stable and reliable. I one time spent a week in a studio trying to sync an old MCI 2" 24 track to ADAT's. I would only work for maybe one pass at a time, then the next time, no sync for more then 20 secs. Very frustrating.
Your R2R is the weak link. If it has an excellent stable motor for the tape transport, you will have more success. But if the motor fluctuates quite a bit, syncing will be a nightmare.
Ed