Does anyone have any recommendations on good Shipping Address validation apps for Netsuite that don't slow down the system a ton?

If you want something that keeps NetSuite running smooth, SmartyStreets is solid for US-based setups, light and accurate. For global use, Loqate works well but needs fine-tuning to avoid lag. AddressTools (Celigo add-on) is also a good pick if you’re already using their ecosystem.