Multi-split options for old row house

I live in central Virginia and have an old 2-story ~1500 sqft masonry house built in the 1890s. It has ductwork for heating on the ground floor but nothing going up to the second floor, presumably because it's a pain to get ducts upstairs with no thick internal walls and only masonry on the outside of the house. I have forced air heating on the ground floor and the upper floor warms up "okay" from the ground floor heating.

I'm looking to install AC across the house and get some additional heating capacity upstairs. I'd rather not tear up all my floors to install ducts, so I've been looking at multi-split systems. I'd like to put three indoor units upstairs and one (large) or two of them downstairs.

With all that out of the way, here are my questions:

1. I'd really like to try to stick to the ceiling cassette type of indoor unit to keep the systems subtle, but I don't know how deep my ceilings go and how deep they need to be. By measuring around by stairs, I estimate that there's about a foot of space between my downstairs ceiling and my upstairs floors. Is that enough to accommodate a ceiling cassette indoor unit? Another complication is that I don't have an attic, so I honestly have no clue how much space is between my roof (flat, slanted, metal) and the upstairs ceilings. Is there an easy way to figure that out without poking a hole into the ceiling and jamming a rod into there? Given that the roof is slanted, I'll need to measure it in several locations.
2. Does anyone have a sense of how much money a project like this would set me back? I've found a few multi-split installers in the area but nobody ever seems to put pricing information up on their websites, and I'd like to learn more about this stuff so I can ask more informed questions.
3. Should I just bite the bullet and look into ducted systems? I find it appealing to get individualized control in different rooms, but I also have a couple of defunct chimneys integrated in the masonry that might be able to hold ductwork without too much trauma to the rest of the house.
4. Are there options for HomeKit integration with these sorts of systems? It would be nice to be able to control the new units with my existing thermostat.

Thanks in advance for your help!

submitted by /u/hvacn00b
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