16 foot you hardly notice it more than a 12 foot.
18 you notice it, but don’t need to much different when driving
20 hours notice it, and have to start making wider turns. Slight experience is needed.
24 foot, you need a skilled driver.

The width you choose is equally important. We have a bunch of 20 foot x 8 trailers. They don’t make those any more, you get an 8.5. Well out less than perfect drivers have had minor accidents and dented those trailers over 7-8 years. So we decided to try a 16x7. Most drivers report back that it’s much easier to drive around and they like it. However it requires flipping the plat forms up on the grandstand if you’re going to bring 3 machines. So in hindsight we should have purchased a 18x7

 

Currently running a small 6x12, but I'm considering upgrading to a 7x18 tandem axle, mainly so I can mount a debris loader + mower + stand on blower all on one trailer for fall cleanups.

I went to check out a 7x18 in person and honestly… it looks massive. For those of you running trailers this size, how do you like them? Do you run into issues navigating tight spots—like backing into driveways or turning around at the end of small cul-de-sacs?

Would appreciate any input or real-world experience before I pull the trigger.

Going to a 7' wide trailer the biggest difference you'll notice is the axle width, the length not so much. I pull a 7X14, 7x20 and a 8.5x32 GN, the longer the trailer the easier they are to back up and of the 3 the GN allows you to turn tighter.
I would recommend brakes on both axles and a tongue jack that swivels so it's out of the way of your tailgate and won't snag the ground and bend.

 

Always upgrade the axels. Minimum 5200 lbs each with both brakes.