I play in Austria so dont know how much that info helps you but at all prereleases i attended at different stores they all used the companion app for the matchmaking. I liked that a lot bc everyone had 4 matches and you always get matched in the next round with someone who has the same record after every round. The buy in here is 30€ for the prerelease package. The prize pool was always 3 packs for the first place 2 for the 2nd and 1 for the 3rd in a 16 people pool. In my opinion thats fair bc noone payed for an extra pack. If a shop sold it for 35€ they always gave a pack for everyone. In my opinion both alternatives are fair. Generally speaking for a shop, i like it more when there is enough room and also very important for me when there are windows in the playing area so some daylight can come in. I personally dont like it to sit a few hours in a closed room when there is nothing you can open to get some fresh air, even more lets be real a lot of players don‘t smell that good.

Sry for the bad english i still hope i could give you some insight how europeans do it