If Harry Kane leaves England for another league in another country, it will be great for him because he will have a lot of interest from big clubs and his buy out clause will be very large.
Going to Real Madrid from England is not a feasible option that can occur immediately. Last time I checked, Real Madrid needed a very talented and young striker like Haaland to take over for Benzema, who is likely to retire soon.
Even if Harry Kane signs a contract with Real Madrid, I doubt he'll stay there for long due to the intense football Real Madrid may require, which he can't provide given his age. If he’s looking to retire soon, he should go for a smaller clubs in other divisions too.
In my opinion 29 years is not old yet, Harry Kane is playing at a high level, he's in shape and he can still play for some years.
This is the best opportunity for him to evolve and try La Liga and Champions League. I doubt Tottenham can offer him the same chances, Liverpool, Arsenal and City are better in this season and I don't see Tottenham fighting for national title or at least the finals of UCL.
In Real Madrid he'll have strong support to play with players like Vinicius JR and Rodrygo to assist him and score more goals in La Liga.
And I don't think he's going to retire soon.
He's only 29, he can play another World Cup easily. I don't think he should go to smaller clubs, there's 3 clubs looking for him: Manchester, Bayern and Real Madrid.
Look at Benzema and Modric, both older and look what they did last year in Real Madrid.
It will be very interesting to see him play at Real Madrid.