The Newcastle team performed well last season. However, the Newcastle team will want to do something new this season. Even though this team does not have the best players, I have enough faith in the team.
Next season Newcastle will appear in the Champions League so Newcastle need to increase their strength so they can compete with other strong teams. Because in the UCL all teams will give their all to be able to compete for the championship, as well as in the Premier League for next season where several teams that were maybe a bit weak will become strong again next season. In order to be able to take their best position in the standings in order to qualify for the UCL in the following season.
As you said, next season will be much harder for Newcastle because they are going to race to win Premier League and the Champions League at the same time but still, I don't think if Newcastle will put too much energy into the Champions League and there won't be too much chance for them to win anything in the champions league, however the got rich owner and they could buy many players not that tournament but I think Newcastle will just focus on the premier league.