Voltage drop is a real thing, especially if you’re running a bunch of low-voltage lights over a long distance. I’ve seen those kits work fine for short runs, but once you get past 75 feet or start stacking on more fixtures, you’ll definitely notice some lights getting dimmer at the far end. Honestly, I’d recommend upsizing the wire gauge if you’re set on wired—don’t just trust the kit wire unless your run is pretty short.
As for splicing, I’m not a fan of just burying connections, especially around gates or corners where things can shift or get wet. I usually run the wire along the fence (tucked up under the rail if possible), and use gel-filled connectors for any splices. It’s a bit more work, but you won’t be digging up your yard every time something shorts out. Those pre-made kits are tempting, but they’re not always built to last if you want a really clean, reliable setup. Just my two cents—sometimes it pays off to go a bit custom instead of relying on the all-in-one kits.