Check the Temps--Hand Will Do
A key indicator to monitor is your tires' temperature. A periodic walk-around, checking tire temps with your hand, can tell you a lot.
For instance, check your tires' sidewall temps using the back of your hand, before starting out. Drive about 10 miles at your chosen speed, stop and then check the sidewall temp again. You should be able to touch the tire w/o discomfort. Depending on ambient temp, they may or may not be all that warm.
The human threshold of pain is about 160F. If you cannot comfortably hold the back of your hand against the sidewall, you need to immediately change what you're doing to reduce internal tire-flex friction-generating heat: slow down, lighten your load, and/or increase PSI.
If you've not done this before, drive another 10-15 miles, and check again. And, perhaps yet again. Experiment with checking tire temps and you'll get a feel for how your vehicle behaves under different situations.
When towing, particularly on long distance trips, I'll walk around and check tire temps at every rest/fuel stop. It'll tell you a lot. Consider a SUV and dbl-axle trailer. The SUV front tires are generally coolest; they're just steering and holding the front end up. Rear tires are notably warmer, they're carrying trailer tongue load and providing driving force. On a dbl-axle trailer, if you have more load forward (all else, like PSI, held constant), the front axle tires will be warmer than the rear because they're carrying more load. Side to side, tires on the same axle should feel the same.
On couple occasions, I've found a leak simply because on a walk-around I found a tire that was noticeably hotter than it should be when compared to the others.
