Worst case scenario, 2 passengers and 2 “empty seats”. So yes most any Uberx should be able to accommodate at least 1 Suitcase in the trunk (I can handle 2–3 depending on size, in addition my stuff), but you can also put a suitcase in the middle of the rear seat between the passengers and another in the front.
The main difference between UberX and UberXL is that an UberX car can only fit 4 riders and an Uber XL car can fit 6 riders. Uber X - Uber's budget option. When you select an Uber X car, an everyday car with seating for up to 4 people will arrive to pick you up. Uber XL - The Uber X for SUV's.
UberX is your basic sedan. So, generally trunk space or hatchback. Estimate what you can fit into an average trunk and pack accordingly. If you need extra space, order an XL which is usually an SUV.
While there's documentation by Uber around this, they do mention about carrying a reasonable amount of luggage per person. Ideally it's 4 medium sized bags per vehicle. Anything more would require booking a larger vehicle like an suv or xl. An XL vehicle can accommodate 3 large suitcases easily.
Uber drivers are never required to ask if you need help or assist you with your luggage. Due to changing travel requirements, many Uber drivers may feel it is better to remain in the car rather than helping with your bags. Your Uber driver may offer to assist with your luggage, but don't expect them to.
If you order UberX or UberSELECT or UberBLACK, you are charged the same fare whether there are 1, 2, 3, or 4 passengers. If you have 5 or 6 passengers, you need to order UberXL or UberSUV.
So what's the difference here between Uber Comfort and Uber X? Uber Comfort drivers need to maintain a rating of 4.85 or higher. Uber Comfort vehicles must be newer vehicles, no more than five years old, with more head and legroom than vehicles eligible for UberX.
What Is UberXL? - A Budget-Friendly Choice for Up To 6. The ride options on this page are a sample of Uber's products, and some might not be available where you use the Uber app. If you check your city's web page or look in the app, you'll see what rides you can request.