Welcome! I've not yet tried buttons or snaps on a self-made kilt, because of an experience with a purchased Union Kilt. Very nice piece of work, but with snaps at the waistband. At the time, Bob was right at 40 waist, but the Union Kilt 40 was just a tad too large -- took a belt to keep it up, and wrinkles from the belt tightening over the snapped waistband. Now that I've been cooking for him the better part of a year, I'm afraid the snaps might not hold :o) I think buttons are similar, unless you put in multiple buttonholes for adjustment.

Velco is your friend. Nice and forgiving of waistline fluctuations, within a certain range. And it all stays hidden behind the belt.

Straps and buckles have as much or more adjustment, if you look at the distance between holes on the strap. I've hand-sewn with leather straps/buckles and there is probably 4 inches of 'give' if you take both straps out to their loosest point.