So I have a ’16 LX570 and had many of the same questions last year before renting my first travel trailer. Outside of 1 or 2 posts across all of the forums, there was very little info WRT towing heavy with a late model LX.
My trip was from SLC...
The level check is more complicated than a dipstick but nothing a competent mechanic hasn't dealt with before. Basically you overfill the transmission a small amount and let it warm up to the point that with the fluid expanded (from temperature)...
Frustrating but you CAN NOT use Tundra mirrors. I read this as, you know "100% sure" so I rolled the dice on some ebay tundra mirrors and the mounting base is totally different. Not even close. Hopefully this saves someone else the restocking...