...But what would you check for, if you were to trade a token on premarket today ?
The main disadvantage of premarket, in my opinion, is that you have to freeze your funds indefinitely, as the TGE date is often not known. But if I receive an airdrop for activities on the testnet or the mainet, then I try to sell tokens on the premarket, as the price usually decreases very much after the pump on the listing.
To add more, the other disadvantage is lack of transparency in aspect of the technical side of the project, devs can still change around the tokenomic putting pre market buyers at risk and if the developers are somewhat grifty, they can inflate total supply and your money become 1/10 of what it is supposed to be since you're already in buying contract that will be fulfilled in the future.
I can't see how people can make money in pre market other than pure speculation.