What to look for in posies and small bouquets
Small hides nothing
On a large bouquet a weak flower disappears into the mass. On a posy you are looking at a handful of stems from a metre away, so every head is on show and one poor bloom drags the whole thing down. This is the category where realism matters most for what you spend, and where it is worth paying for fewer, better stems.
It has to look right from every side
A posy usually sits on a bedside table, a windowsill or a downstairs shelf, which means it is seen from behind and from above as often as from the front. Many are built face-on for the photograph, with the good flowers at the front and the back left flat. Look for a photograph from another angle, or at least check the description does not call it a front-facing piece.
Match it to a vessel you already own
At this scale the vase is half of what anyone sees, and a posy in the wrong container looks worse than no flowers. Measure the neck of the jug or bud vase you intend to use before buying, because a tied posy cannot be spread out to fill a wide opening the way loose stems can.