Not quite equal. At its peak Bitcoin Cash was about 25% of Bitcoin, and at a much lower price too. If you reinvested it at exactly the right time, you could multiply total yield by 1.25, but that's a big if.

Yeah, Bitcoin Cash is nowhere near its peak ~4 years ago, when it was like $2500 (it's $824 a coin this morning). It has not kept up with Bitcoin at all this bull run (although it has gone up, just nowhere near at the same rate). So yeah it'd be nowhere near double today's Bitcoin value.