I don't know of any 401k that has a guaranteed rate of return of 8%. I think you are misunderstanding both 401k's and RRSPs.
No. You misunderstand what a RRSP is.does Canada have some sort of rate of return?
And you are misunderstanding how withdrawals work.and also withdrawing funds from a RSP would be hefty even in 20 years
If you take a withdrawal it is the same as if you earned it as income.
You probably want to do some reading, to understand the basics of Canadian personal finance. May I suggest Personal Finance for Canadians for Dummies. It covers the basics well.