Processing b&w is so easy and likely much cheaper and certainly subject to all the controls you want. For instance you can use TMAX100 as ISO100 and I have seen it used up to ISO1600 - push processing. You can of course have labs push process for you too.
What you most likely will have to get used to is the metering of the X-700 or other cameras of the era. The huge latitude of most all C41 and b&w films is most forgiving particularly on the overexposure side. If you don't process your own b&w, perhaps you should consider using chromogenic film - b&w film that is processed like regular C41 film, like Kodak BW400CN and others.