What impact does COGS (and my COGS %) have on taxes?

The larger the COGS % means the larger the expense you will have on your P&L.

If you’re operating at a profit, then as your COGS % increases, it decreases net income and therefore decreases your taxes.

If you’re operating at a loss, then as your COGS % increases, it further increases your loss. Generally speaking, you'd only pay taxes on your profits. But if you're at a loss, then you shouldn't have tax to pay.

Further thought…

COGS is booked when you make a sale. That COGS booking reduces your Inventory Asset. So the larger the COGS %, the more Inventory Asset balance will be deducted.