A dark suit waistcoat adds a clearly visible central button line beneath the open jacket. The pale shirt frames a blue tie with small light motifs and diagonal lines. A pale folded pocket square provides another accent at the upper side of the jacket. The photograph concentrates on torso and hip, without fully including shoes or head. One hand rests in a pocket.
Compare the additional front here first. Do you want another dark surface between shirt and jacket, or do you prefer the more open arrangement without it? Try both possibilities on the same suit where the offered version allows that choice. Keep shirt and tie reasonably consistent so the difference created by the waistcoat stays visible.
Sit with the actual shirt and observe the transition towards the trouser waistband. Remove the jacket too if that is part of your office routine. Only then can you assess the waistcoat as the independently visible front. Add the pocket square last. The close photograph is useful for these line comparisons but requires a further complete view for trouser length and shoes.