With heat pumps you just set the desired temperature, and it’ll send warm air or cool air accordingly.
At that time (in our little two-bedroom house) we got a ducted system made by Fujitsu, with a single outdoor unit going to an indoor unit in the roof space, which ducts to ceiling vents into all the main rooms together. It was a bit expensive but one of the best things we ever did in that house, as it regulated the temperature throughout the house very quickly and we could set up timer schedules for it.
Our current house was tricky, as the ceilings are high (so the air volumes are large), and the house is on multiple levels; but in the end (after a winter and a summer to get used to the house) we again got heat pumps put in, despite the fact that it wasn’t as ideal as our last house. (We moved houses in the middle of Winter last year, and the first morning in the new house was a terrible shock – I’d forgotten what a cold house was like! We made do with the fireplace for the rest of the season, sweltered through summer with all the windows and doors open, and then did something about it…)
Ducting wasn’t an option here, but upstairs we have a single outdoor unit piped through to multiple indoor wall-mounted units (one per room, controlled independently); and downstairs we have a different outdoor unit for a single indoor wall-mounted unit (layout is awkward, so we did what we could). Upstairs works a treat; downstairs was a really big ask given a really big open space, but it worked out as well as we could have hoped for (and the fireplace is downstairs, so heating can be a team effort). We ended up with two different manufacturers (Fujitsu downstairs, Daikin upstairs), for reasons related to the differing requirements of the spaces.
I gather that Fujitsu tends to be good when it comes to replacing parts with minimal fuss if there are any issues (at least over here, and according to our contractor), but we haven’t had issues with any of the units in either house, so I can’t really say whether any given company is better than any other.
Not sure if any of that is really helpful.
My one piece of solid advice – deal with companies who will send actual heating engineers around to spec out the requirements. If you get a cheaper-but-underpowered unit it may end up working overtime all the time, and be inefficient. As I understand it you want to err on the side of over-speccing these things, and you want to trust that the person you’re talking to knows what they’re talking about.
In the old house we talked to two companies initially and the quotes were so massively different that we got a third company to quote as well so that we could figure it out. The cheap quote was from a salesman. The two expensive quotes were from engineers. By the time we’d talked to everyone and learned some stuff, I did some research of my own, and came away convinced that the cheap option would have been a mistake for us, and that the salesman was just trying to get a sale rather than assess our actual needs.