Will it be safe to use Electrum BTC and Electron Cash wallets with the same address on the same PC?
Or it will be better to create new BTC wallet in Electrum?
As far as I'm aware there have not been any reported cases of people losing BTC or BCH if they use the "official" wallets from the "official" websites.
Having said that, it would probably be prudent to use different wallets, with different addresses. If nothing else, it will help with your privacy across the two chains. Unless you have a very good reason to continue using that BTC wallet (for instance, expecting payouts to old addresses) then you should probably create a new wallet.
TL;DR:
Is it necessary to create a new wallet? Probably not.
Would it be wise to create a new wallet? Probably so.