On tapping up, there's basically a gentleman's agreement in the Premier League. If you're interested in another club's player, the club chairmen (of maybe DoFs) will have a chat about it. If the chairman at the target club says no way then everything has to be done officially - you agree a fee and only then do you speak to the player (although obviously you can speak to his agent in the meantime). However, if the chairman at the target club doesn't kick off then it's understood you can approach the player and agree a fee later if he's up for it. If you get caught and if there is evidence you are bang to rights then you back off and / or end up paying extra to persuade the target club not to grass you up.
The position with foreign clubs is more difficult, but again the general principle is that you don't speak directly to the player before you agree a fee (exception of expiring contracts where you can do a deal from 1 January). But it's all about proof, and invariably it can't be proved, so a settlement fee is common, and that's what I think happened with Trent.
But if, hypothetically, you were to fly a player from the South Coast to Blackpool Airport for a face to face meeting with his prospective new manager, the flight were paid for by the buying club and the flight manifest disclosed who was on board, and then he and the buying club's manager had been spotted together at the airport, well it would be difficult to argue you hadn't engineered a meeting that was against the rules, and if the FA asked to see the flight details in response to a complaint by the target club then there would be clear evidence. In that situation, you'd have to back off and then pay a bit extra when you did the deal properly a few months later.
But if you were being super sneaky, you might host, say, Mbappe, on a flight on your owner's private jet flying around the Nice area (because he was at Monaco at the time) whilst having a chat on-board. In that situation, the club wouldn't have an invoice or access to a flight manifest that would prove what had happened if there was a complaint.