Could I use models on CGtrader in a game commercially?

It depends on the License of the model. You can see it on the right side on model's page, under the Licence tab. There are some blue links you can click on and read, what you can do and cannot do.

The basic rule of thumb is that you cannot make money from the props directly.
E.g. sell it as an in game asset (for example, game player must pay a fee for having the item to use in game).

Or you make some kind of mod kit and include the stock media to boost up the overall appeal of the kit and sell it or distribute it for free.

Basically the asset needs to be constituent of your game "only" and preferably in a proprietary format.

Best to only just use it for some additional added value of meaningful work already done.
From game developer standpoint I would not exceed more than 30% stock media use.

The "General License" allows for stock media to be used for inclusion in commercial games, but it also specifically refers to the obligation to safeguard the proprietary ownership and interests of the original authors.

This is indeed a bit of a gray zone and there is some room for interpretation, but the original author will always keep power to take things to cord and let a judge make decision about possible copyright infringement of the intellectual property in case of a dispute between the two parties.

Short story, we will not have any problem if we all benefit from our efforts, misuses resulting in downgrading the efforts we do will surly lead to problems.