This is a viable plan. This way is definetly secured as long your computer is not compromised and you don't fall for any faked/compromised wallet software.
To pretend a replay attack you would have to send your BTC (currently sitting in your electrum wallet) to a new (3rd) wallet.
At this point your BTC's are safe. The only transaction which could be replayed at this time would be the TX to your (new) wallet on the BTG chain.
And this wouln't harm you at all. So your coins are safe in this scenario.
Thanks bob123, appreciate your help. For the 3rd wallet, I will send to exchange after the B2X fork and buy some alts.