For a given pedal force the chain is under less tension when using the biggest chainring (think of a lever from the pedal spindle to where the chain runs). This also means less force on the sprockets and if using a small sprocket it also means less force/torque on the back wheel.
Edit: As Peter Cordes in the comments added: For a given sprocket and speed (i.e. power output) the chain tension will be the same, independent of the chainring. With a small chainring you’ll pedal fast and lightly while with a big chainring you’ll pedal slow and powerfully but the chain will move at the same speed and will be under the same tension. Pedaling slow but powerfully will of course put more load on the pedals, crank arms and bottom bracket.
The highest load possible is probably when you accelerate with all your power from a standstill using the smallest chainring and largest sprocket.
You can try to minimize wear by using a relatively large chainring + relatively large sprockets. The larger the chainring/sprocket the slower it will wear, since there is more material (assuming they are all made out of aluminium, sometimes the smaller ones are made out of steel for this reason).
I dimly recall a test in a bicycle magazine where the larger chainrings allowed for more efficient power transfer, which is interesting because the rear derailleur’s spring will put the chain under slightly more tension which should actually increase friction and make it less efficient. They theorized that this increased tension resulted in reduced vibrations, which in turn increased the efficiency.
All that being said: Use a gear where you feel comfortable and can pedal at a fast enough speed, otherwise your knees and other joints will suffer and you’ll tire faster. Generally >70 crank rotations per minute are advised, with ~90rpm often considered the optimum. Bicycle parts are easier to replace than joints.