Some routers have limitations on DHCP reservations, but higher-end models or custom firmware like OpenWrt can offer more flexibility. If TL-WA1201 V3 doesn't specify a limit, it might be best to...

The EAP110 Outdoor should work well for getting a strong signal outside, but since WiFi struggles with walls, you might still have weak spots inside the garden room. You could pair it with a second...

A small weatherproof awning or a DIY cover made from a plastic junction box and shades could work. Just make sure it allows for good airflow to prevent overheating.