There are many things to think about when deciding what vehicle to tow behind an RV. Using an existing vehicle, finding an ideal tow vehicle, weight, braking, ease of use, and costs involved are all things to consider.
In general, a vehicles transmission or transaxle must either be disabled or lubricated to tow it. There are several methods available to perform this function.

Tow Dolly
I refer to towing a vehicle with all 4 wheels on the ground as “4 wheels down”
I will start with tow dollies. A tow dolly is a 2 wheel device with a platform and ramps that attaches
to your RV’s tow hitch. A dolly requires attachment to your RV, driving your tow vehicle up the ramps
to the platform, latching the dolly so the ramps are in a locked position, and strapping the tires to secure
the vehicle to the dolly.

I consider towing any vehicle backwards on a dolly dangerous and do not recommend it therefore;
a rear wheel drive vehicle would require additional equipment to be towed forward on a dolly.
There are several varieties and a number of dolly manufacturers. A basic dolly has fixed platforms.
Upgraded models have swivel platforms, and top of the line models have wheels that turn.
I recommend either swivel plates or turning wheels because when turning while towing, the front wheels
on the towed vehicle will try to turn even though they are strapped to the dolly. If the platforms or
wheels on the dolly do not move (fixed platform) the towed vehicle wheels will bind causing
the hold down straps to loosen or the vehicle to shift on the platforms. Many vehicles can be towed
using a dolly. In general front wheel drive works best and you must have a vehicle that is not too
wide to fit the dolly.
In my opinion, a dolly works well for someone who wishes to tow more than 1 vehicle
since the towed vehicle does not require any additional items to be towed.

Options for dollies include a folding feature to make them more compact for storage and brakes.
Brakes should be considered and may be required by law. Towing laws vary by state and
your state laws should be checked prior to purchasing. Be sure to purchase your dolly
with brakes if required by law since brakes are difficult and expensive to add later.
There are many reasons a dolly is not the preferred method.
Dollies do not tow as well as a vehicle with 4 wheels down.
Dollies are a hassle to park and deal with at campgrounds. Dollies take longer and more work
to load and unload than connecting/disconnecting a 4 wheels down vehicle.
Hold down devices (straps) are a constant worry.