I've never had a true bespoke experience, but since no one else has responded I'll take a shot. Among the "hallmarks" of bespoke tailoring are a high(and often small) armhole, sometimes a tapered sleeve. Pants vary widely, from baggy, almost zoot-suit style to closely fitting. As you said, manufacturers often make low, large armholes and low trouser forks to fit a wider range of people, but for bespoke they should be able to make a garment as best fits the individual. They should be able to place the armhole as fits the person, size the armhole accordingly, and maybe taper or fit the sleeve to fit the person's arm. I like low forks on my jeans. But I like my dress pants not to be ridiculously baggy but also not uncomfortably tight.