I've been using a Magic Keyboard and Magic Mouse 2 with my Late 2013 iMac for quite some time. Other than the need to charge, I've detected no differences compared to a wired mouse/keyboard. The fact that they pair with a USB/Lightning connection rather than traditional Bluetooth pairing is a plus, and rechargeable is a huge plus compared to replacing AA batteries.
All that said, the simplicity and reliability of a wired mouse and keyboard is hard to match. The trick is finding them if you need new in an emergency. Generally what's available at the local Best Buy is their ultra-cheap, house-branded stuff. It'll get you by in a pinch, but that's about it. If you're shopping around for the best feel it's really hard to avoid Bluetooth.
In all honesty, I've had very little in the way of connection problems with all my various Bluetooth keyboards (which include those I paired with my first-generation iPad more than 10 years ago), and a wired mouse/keyboard remains a useful item for the tool kit when trying to revive an ailing PC.
The trick with wireless anything is that its affected by your local radio signal environment. If you have nearby, strong sources of radio interference, you're going to have issues. All computing gear generates RF, and while using a Bluetooth keyboard near a CPU is expected use, the presence of additional gear (or even a microwave oven) can throw a monkey wrench into the works. I isolated one person's Bluetooth connection issue to a Wi-Fi router located in a drawer directly below the computer desktop. In the old days of analog radio broadcasting we called that "swamping the input of a receiver's front end."
I can tell you tales going back nearly 50 years... Such as a designed-in-suburban-Silicon Valley (Redwood City) Ampex MM1200 24-track audio tape machine that did very poorly in the high RF environment of Midtown Manhattan (such as the radio and TV transmitters in the Empire State Building). The machine didn't meet low-frequency noise spec (hum). We initially thought it was due to 60-cycle power line pickup, but it turned out to be demodulated 59.94 Hz video sync from those TV stations, picked up by the unshielded wires running from the playback head stack to the playback cards. Properly shielding the cables turned out to be too hard to accomplish (long story). It was easier to add an RF choke to the input of every playback card, which licked the problem.
