Red Velvet White Chocolate Cheesecake Trifle

[16.25] oz box red velvet cake mix plus eggs (oil and water to prepare)

White chocolate cheesecake mousse:

[12] oz whipped cream cheese

[3.4] oz packages instant white chocolate pudding

half & half

pure vanilla extract

powdered sugar

Ganache:

[11] oz package white chocolate chips

heavy cream

Topping:

sweetened fresh whipped cream or 1 [16] oz Cool Whip

[4] oz white chocolate bar

chopped pecans (toasted and divided)