Well, it’s not very often you would hear one of the groomsmen giving a speech at a wedding reception unless that groomsman is the best man. Often a best man is referred to as a groomsman and thus when somebody mentions about groomsman speeches or groomsmen speeches he is most likely referring to best man speeches.
But not always. There are weddings where each or at least a few among the groomsmen address the guests with lovely wedding speeches. And why not? It’s not mandatory for the groomsmen to deliver speeches at the reception and nobody expects them to come up with one. So, it would be a great surprise if one or a couple of the groomsmen decide to toast the newlyweds. That would be a nice idea to make the entire wedding speech session even more interesting. Even better if the groomsmen keep this as a secret (especially from the groom) and can only share it with the MC or the best man in advance.
The best time for groomsman speeches would be right after the maid of honor speech assuming that there isn’t any speech left after the bridesmaids have spoken. In other words a groomsman speech should come at the very end of all wedding speeches. And it wouldn’t be a good idea to have best man speeches and groomsman speeches back to back.
However, groomsman speeches shouldn’t be typically very different from best man speeches. This is simply because the team of the groomsmen comprises of the friends, brothers and cousins of the groom and the best man is just one of them. And keeping in line with best man speeches, you would also want the groomsman speeches would to be humorous. But it is very important that the groomsmen make it sure to keep the speech super short because the guests already have listened to enough wedding speeches and should be dying to rush to the buffet tables by the time they get the chance to speak. Ideally the best speaker from the groomsmen should prepare himself for the groomsman speech on behalf of the entire team.