QuickBooks physical inventory tracking is not complex. If you buy things and simply re-sell them, then QuickBooks will meet your needs. If you are a manufacturing company or you are transforming raw materials into goods then QuickBooks online inventory tracking will likely be insufficient.
QuickBooks requires you to use the first-in-first-out (FIFO) inventory valuation method. It’s possible to use LIFO or the average method, but I will not discuss that here. You can’t track physical items in QuickBooks until you enable the Track Inventory Quantity