thank you for the reply, so basically setting gas higher than suggested won't matter?
If you are setting your gas higher than suggested that is if you are trying to do a normal transaction which uses gas of 21000 with placing a gas of 100000, then you need to pay a higher transaction fee than expected.
It seems you're a bit mistaken here.
If you're trying to send a usual ethereum transaction, it requires 21,000 of gas. If you set the gas price at 20 Gwei, your wallet balance will be debited by 21,000 x 20 Gwei = 0,00042 ETH and that amount will be taken as a reward by miners.
If you set 100,000 gas limit for the exact same transaction with the same gas price, 20 Gwei, your wallet balance will be debited by 100,000 x 20 Gwei = 0,002 ETH. BUT, all the 0,002 ETH amount won't go to the miners as a fee, they will still get 21,000 x 20 Gwei = 0,00042 ETH for the mining and the rest 0,002 - 0,00042 = 0.00158 ETH of the previously debited amount will be refunded back to your wallet balance. This way you always pay 21,000 of gas for a usual ethereum transaction no matter what gas limit you set.
Gas limit which is set above the required threshold don't affect the transaction fee in any way and don't make it higher.
Like you say, incorrect gas limit can make you pay useless fee if you set the gas limit below the necessary limit, but not if you set it higher.
Consider the gas limit like a spending limit for your usual wallet. It's like paying with a $100 banknote for the good which costs only $21. You will get your $79 of change back in any way, becasue the good costs only $21.
What does affect transaction fee and transaction confirmation time is only the gas price.
