Hi Mel,
I've had mine for a year and have no complaints at all. I can't comment on towing capacity as I don't tow anything, or what the previous model's engine was like - but I can certainly say the current model RX's engine is absolutely fine - fast when you want it to be and smooth and quiet when you don't.
As for trim levels, I guess it depends on what your priorities are and what is important to you. I have what is equivalent to Luxury spec, but it still comes with heated/cooled seats, heated steering wheel, radar cruise control, reversing camera, etc. F-Sport and Premier add niceties such as ML audio (optional on F-Sport I think), adaptive suspensions, 360 degree cameras, HUD, blind spot monitoring etc. Panoramic or sun roofs are optional on all grades as far as I know.