i would simply try to use the HA itself as the controller with some rules you setup.
you prob. will aim for a target temp anyway, lets say 28C room, leaftemp is usually 1.5-2C lower.
so you integrate your heating in some way.
electric heater with a smartplug, a radiator can be steered with a zigbee thermostat f.e.
quite a lot ACs can be integrated too in HA.
for the humidity similar aproach, prob. humidifier by a smart plug is the easiest.
then you setup your automations in HA.
you can simply setup several conditions if needed, like set a certain speed for your inline fan if heating is on f.e., or a certain min max percentage the inline fan needs to run before takin other actions.
ideas come over time and a bit trial and error will get you there for sure.
good thing is there is hardly some you cant integrate in to HA and setup a automation for it.
for the AC infinity stuff i found this on the quick.
AC Infinity integration for Home Assistant for UIS based controllers - dalinicus/homeassistant-acinfinity
github.com
as said, i have no overview of their proucts.
on a quick look i havent found how they deal with the leaftemp, they may skipped it? (bad).
if they skipped it, i would go with the vpdchart.com calc or base your vpd on this below anyway
Now, the plugin is installable via HACS
community.home-assistant.io
no real need for their controller exept the fanspeed setting which may can be achieved cheaper anyway.
btw. i could get away with a non controllable inline fan so far, i would use its speed settings if i could, but it have no interface.
as its used as a scrubber only, steering the whole room have way more effect anyway for me.