PSG this season seems to have no competitors to win the Ligue 1 title, they are too strong compared to other clubs. So, I think PSG this season will only focus on the UCL league rather than Ligue 1 because without any hard work they will get the Ligue 1 title this season.
Nice is indeed good this season, but that is not enough to be a competitor to PSG because as you said they are only strong in defense but in scoring goals they are having difficulty. This can be seen from the 17 matches that Nice has played they are only able to score 19 goals, this is small compared to PSG, Monaco, Brest and Lille.
PSG at the moment seem to be enjoying some monopoly in the Ligue 1 been the toughest and the top team at the moment but then it's not enough for them to become lax els they have the likes of Nice and others who will be ready to displace them at the top position almost immediately, they are five points apart which isn't much for nice to cover.
If Nice wwins their next three fixtures, it's very much possible the will be at the top of the table is PSG loose two or three games at a go.so there are still possiblity of other teams getting to the top tho it's slim but then PSG have got the UCL to face so I think when they resume the round of sixteen at the UCL they will be a bit distracted at the Ligue 1 a d that will definitely be an opportunity for others especially NICE who would want to cover up the gapto the top of the table.
It is not easy for other teams in League 1 to break PSG's dominance as long as PSG still has Mbappe and the strong squad PSG has still won the League 1 title. Nice is also a strong club but not as strong, although at first it was able to beat PSG, but Nice is not that consistent winning was different from PSG, which initially was not very stable at the beginning, but at the end it was able to provide strong resistance and now PSG has started to focus on achieving victory after victory to continue to widen the gap with Nice. Moreover, Nice is not that much of a pressure for PSG because PSG knows the club that started it performing well in League 1 did not last long to maintain its performance.
In the 3 matches that Nice will face it seem quite tough, Nice will face Rennes away, Metz at home and Brest away, we all know two of them like Rennes and Brest are quite tough matches because Nice is playing away so we don't can predict with certainty whether Nice can win in 3 consecutive matches, especially if PSG suffers a defeat, it seems that this will most likely not happen because PSG is already on the winning path.