FPs who get traded to other NHL teams within real NHL

[Rangers GM (Steven)]

I am wondering what happens when FP players get traded to other teams in the real NHL. Do owners need to select new FPs from their team name rosters and how does the salary rule of 15M apply with players(FPs and ex-FPs traded away)?

[Ducks GM (Holden)]

how this happened with me. jamie drysdale got traded and i had till the start of the next season to find a new FP. his cap hit didnt change and my new FP (Cutter Gauthier) also has to fit in the remaining 15 M.