Whatever terms two parties agreed on, the deal is dead in the water unless there's an independent body that determines whether a party violated the agreement or not. Otherwise, the deal will function up to a point when one party's opinion is in disagreement with the other party's. I remember, Brexit backers said something along the lines of, "We won't accept the authority of the European Court of Justice, it compromises our sovereignty". What is the dispute resolution authority between London and Brussels now?
It's a mixture of different systems depending on the context.
The UK and EU must each nominate 10 legal experts to form the ‘pool’ of potential panellists. They must jointly nominate five legal experts to serve as potential chairs. When a dispute arises, the UK and EU each select two panellists from the pool. Those four panellists then elect a chair from that pool. The parties must comply with the panel’s ruling within a reasonable period of time. If the offending party fails to do so, it can be required to pay a financial penalty or to suffer the suspension of some other part of the agreement.
The ECJ retains its exclusive jurisdiction over issues of EU law. If a dispute arises concerning an issue of EU law, the panel is required to submit it to the ECJ for interpretation.
EU-UK trade disputes
Under the Trade and Cooperation Agreement (the "trade deal") an Arbitration Tribunal will be formed to sort out any disputes. The tribunal will consist of one legal expert from the EU, one from the UK, and one jointly agreed non-EU/UK citizen to chair it. It is quite similar to provisions in other trade deals like the EU-Japan or EU-Canada one.