It not a competition and no award or ranking was given, as far as I can tell. This is called Spring's Pants [panty] Festival. The first round was 2020, on that day, 25 titles were released by 25 different studios. Customers who purchased 5 titles and sends in the stickers from the packages will receive a lingerie photo book featuring all the campaign girls. Also a few (23) lucky applicants will receive used panty from one of the idols. The videos in this round have their normal video code, e.g. MIRD-201, I collected that vid without even knowing it's involved in a campaign of some sort.
On 2021/03/03, 26 vids, 26 studios, beginning with this round, perhaps because of poor awareness, the video code was unified to PFES (for Pants Fest) but to be honest, I was just as oblivious. Without paying attention, for a long time I w Also i can't find (too lazy) the promotion details.
The second round was released on 2022/03/25. Also 26 videos from 26 studios. Continuing the video codes from PFES-028 onward. For this round I found an official website with mutiple videos:
http://pantsmatsuri.com/
and DMM's page with details of the promotion itself:
https://www.dmm.co.jp/digital/videoa/spring_panties2022/index_html/=/ch_navi=none/
Notice the studios participating don't include Faleno, Prestige, SOD.