So if I assume, that if I split the amount on two receiving wallets, the transaction sizes increases and the whole transaction will be more expensive.
Do we talk here about twice as expensive or 30% more expensive?
Right. The more inputs or outputs you have, the bigger transaction fee you have to pay. Do we talk here about twice as expensive or 30% more expensive?
Assuming your transaction is segwit and it includes 1 input and 1 output, its size would be around 110 vbyte. If you add one more output to your transaction, so that it includes 1 input and 2 outputs, its size would be around 142 vbyte. That's around 30% increase in transaction size and will lead to 30% increase in transaction fee.
You can use coinb.in fee calculator or bitcoindata.science (a tool created by the forum user, bitmover) to calculate transaction size and transaction fee based on number of inputs and outputs.
Awesome, thanks!