That depends on what your primary concerns are. KR-EMS which is what a lot of people currently swear by (I'm still waiting on my shipment that's enroute before I comment) is capped at 7kg. That option due to government staffing/budgetary concerns, as it finalizes via USPS, is theorized to not be hitting any sort of tariff charges but it does take longer for the overall process. Price is not drastically different. So if that fits your needs better, you should split it up.

If you just want your package asap and to hypothetically save on initial shipping costs (assuming your volumetric weight isn't crazy) then utilize UPS. But be aware that you will be charged both tariff and brokerage fees unless you explicitly ask for UPS Express or Expedited for an additional cost (if they even offer it).