I know the towing capacity of a 2014 RX with tow package is 3500lbs. Im curious to know would I be Able to actually tow , 1500 lbs 2 motorcycles plus small trailer safely and efficiently without causing damage to the vehicle?

Not familiar with our manual on our '10, you might see a line on what it can tow without the package in the '14 manual. Dealer may have an answer as well.
Biggest failure with towing is always the transmission. Look into a remote trans. cooler or a larger cooler if already equipped.Don't be fooled, the trans will really struggle with the hot fluid.
Transmission have a nasty habit of just plain quitting after a towing road trip.

The Rx's with the tow package have a heavy duty radiator, and a heavy duty alternator to handle the load. If you tow, you do need to change out the tranny and differential fluid at particular mileage milestones.

We tow a dual jetski trailer with my RX350 - trailer is 1000 lbs, the skis are 750 each, and then 4 gas cans = another 125 lbs or so. So assume 2000 lbs total, assuming skis are gassed up and the trailer box has some tools in it.

You need to plan your braking a little more thoughtfully, and you will use the manu-matic gearbox speeds more frequently, but it's a very capable hauler in general. I wouldn't be worried at all with that trailer and weight.

Thank you both