If you want to start small, I'd go with one supported by Asuswrt-Merlin, "a third party alternative firmware for Asus routers, with a special emphasis on tweaks and fixes rather than radical changes or collecting as many features as possible." Keeps it close to stock with minor upgrades, and a faster release cycle for fixes. The RT-AX88U_PRO is one of the higher end routers that is supported by Merlin.