What are the safest BTC and ETH derivatives?

In my country we can't repurchase the same assets within 30 days of selling them without incurring tax penalties.

So I want to sell some BTC and ETH before the end of the tax year to use my capital gains allowance and immediately buy derivatives like wBTC and wETH so I don't miss out on any gains in the next month, then I'll trade them for BTC and ETH after 30 days (which will be a taxable event if they've gone up, but better to pay some tax on gains than miss out on gains completely).

Are wBTC and wETH the safest options and the cheapest in terms of fees? I use Kraken, so ideally I want to buy everything on there to avoid any withdrawal fees, unless there's a good reason to buy something different that they don't offer.