Backdoor Roth

Every month I have two recurring transfers, initiated from Fidelity. The transfer lands in a Traditional IRA. I can invest the funds immediately but there is a 14-day hold if I try and transfer the cash to my Roth. So, I either purchase shares immediately and then transfer the shares to the Roth, or I wait the 10-14 days and then transfer the cash to the Roth. I am assuming there will be tax implications either way? If the shares go up before the transfer, tax on the gain? And if I sit in cash, tax on the interest earned? Either way, both amounts would be small as I use it to invest in index funds. Am I looking at this the right way?