I like syncthing, but when I was trying it on just 3 laptops on the same wifi network, the speed seemed much slower than what I expected the maximum to be.
Note with Wi-Fi only 1 device can talk at a time and device -> AP -> device counts as 2 devices talking. Now factor in acknowledgements and inter-device sync and you've got a great mash of exactly-what-wifi-wasn't-made-for.
Make sure your firewall is not blocking syncthing ports. You might be using one of the internet proxies instead of your full lan. An easy way to test is to unplug the wifi network from the internet.
(Anecdata I know).