Active cruise can basically control the car down to a complete stop but I’ve never trusted it enough to do it and always end up hitting the brake. Lowest I’ve let it go was from just over 110 down to 50-60 in a roadworks zone before I felt the car in front was coming up a little too quick. It’s been a while since I read the manual but I think the lowest you can set it is 60 although why would you? Use it for freeway driving and then turn it off.
Why would you use LKA (Lane Keep Assist) around town? It’s not worth it, if you can’t keep your lane on suburban streets at low speeds hand you’re licence back and catch the bus

That being said on a more serious note you’ll find LKA (Lane Keep Assist) isn’t as effective on suburban roads as many of them don’t have the marked edge lines like a freeway/highway does. Minimum speed it works to is about 60kph I think.
Not sure of the max speed LKA (Lane Keep Assist) will work but it works fine at 110 on the freeway so shouldn’t be an issue. You’ll find active LKA (Lane Keep Assist) can be annoying/off putting when you feel the constant automated inputs on the steering wheel. I really only bother using it when I’m tired as a back up plan. Same thing applies for freeways as suburban streets re what I said above about catching the bus. Nothing worse than trying to overtake and the numpty in front drifts towards your lane as you begin to accelerate. As for LKA (Lane Keep Assist) and LFA try this link.
Introducing DriveWise - Kia’s autonomous driving and parking assistance technologies.
www.kia.com