I’m planning to build several WiFi connected devices for home automation: an AC remote control and air quality sensors. These devices would send data and be controlled through a local server. I’m considering two approaches: running custom software on a server PC (hardware to be determined) or integrating with Home Assistant’s protocols and purchasing their hardware. Would using Home Assistant be excessive for this use case?


Before HomeAssistant, OpenHab was the undisputed king. I still like them because they let you remotely access you home without having to subscribe to anything or set up any remote access methods
This implies that I am paying to access HA outside my network. I am not. You do not need any kind of subscription to access home assistant externally.
I choose to pay for remote access, but it’s for convenience and to support the developers. You are free to configure it yourself in a couple ways (and there is decent documentation) or do without remote access
I don’t know how you set up remote access for OpenHab, but from a quick glance at the web site it looks similar