With ALL WIDTHS set to 300px using a class,
see the results of different settings for DISPLAY:

Resize the window to see how each behaves at different widths:

display: block; (applied to each item)

Item
Width set to 200px specifically on this item
3rd Item

display: inline; (applied to each item)

Item
Width set to 200px specifically on this item
3rd Item

display: inline-block; (applied to each item)

Item
Width set to 200px specifically on this item
3rd Item

display: flex; (applied to each item)

Item
Width set to 200px specifically on this item
3rd Item

display: inline-flex; (applied to each item)

Item
Width set to 200px specifically on this item
3rd Item

display: inline-flex; flex-wrap: wrap; (applied ONLY to parent)

Item
Width set to 200px specifically on this item
3rd Item

display: flex; (applied ONLY to parent)

Item
Width set to 200px specifically on this item
3rd Item

display: flex; flex-wrap: wrap; (applied ONLY to parent)

Item
Width set to 200px specifically on this item
3rd Item

display: inline-flex; (applied ONLY to parent)

Item
Width set to 200px specifically on this item
3rd Item