The RX350 is a very popular ride in my area. My understanding is that new models whether AWD or FWD all have a tow cap of 3500 lbs if they have the factory tow package its my understanding it comes complete with a transmission cooler etc. If no factory tow pack the AWD version can tow 1500lbs but I dont for some reason think that the FWD version has a tow rating without the package - but not totally sure about that so it could be wrong and may have been just something I was told.
The best way to find out about your Lexus' tow capacity would be to ask a Lexus dealer. They can even check your vin and tell you how it's equipped (tow package or no) if you aren't sure.
Folks here know FG trailers, but not necessarily Lexuses (why does that look like bad spelling to me?).