I'd probably suggest checking out Reddit (r/hvac for pros, and r/hvacadvice for homeowners) -- you'll generally get really good advice, often from professionals

I'd probably suggest checking out Reddit (r/hvac for pros, and r/hvacadvice for homeowners) -- you'll generally get really good advice, often from professionals, if you provide good inputs/context. If you have 2+ floors, you probably need (or have) zones, and it may be worth paying a professional to engineer a solution that meet your requirements. I recall finding some small businesses online that do exactly this for a nominal fee (<$500 IIRC). You might also consider looking for residential HVAC companies that also do commercial refrigeration; the conceptual physics for commercial refrigeration aren't much different from residential HVAC, just specialized refrigerants & components that are tailored to those use-cases (ie labs often require extra-cold freezers, etc). FWIW, my gut is you'd be happy with most variable-speed offerings, if sized appropriately. Low humidity here makes it easier, but I'm sure you can do what you want, but it may not be cheap.