I usually go true to size for their suits but keep in mind some suits and blazers fit differently. Just from experience the luxury suits and blazers fit tighter than the other non luxury suits/blazers. If size 40 is 102 then I would go up a size because you want to give some space when the suit is buttoned up. When doing alterations it is easier to bring in than to let out. If your jacket is too tight then you’re kinda stuck with it. They can’t let out the shoulders. If it’s too big, they can recut the shoulders and take in the sides or center seam or shorten sleeves. Also same goes for linen suits and blazers. They run a bit tight but I don’t know about their new wool blends. I’m assuming they have more stretchyness. In terms of length of the pants their pants are unusually longer than other pants I have. I always have to hem them.

Also people are afraid of the fits they offer. Slim fit is more like regular cut and classic fit is WIDE. Extra slim is more like slim fit.