What wallet or tools can I use to make multiple transactions to 20 different wallet addresses at once? Also I find a tool called cointool app but the gas fee is higher than if I send the transaction one by one myself, is this normal?
The percentage of charge fees you get depends on you coin you are transacting with.
There are network pools that assumes these fees so you can not get precise feedback as no one knows your coins.
As for multiple at a time, that is far unknown to me.