My initial impression is that the Bella spalla trousers are similar to Walts. Slim but not skinny. More of a tailored fit. I went one size down based on the measurements (32 instead of my Walt 33). I don't have any driggs or s&m. I haven't taken them to the tailor yet but can report back after I do.
My only comment, made above as well, is the pockets are smaller/shorter than my Walts. @ehaberdasher said he'd address that with the next iteration.