Just from the very low power consumption of the variable speed compressors in the mini split should make it an excellent candidate for solar power...sorry I cant help on the sizing questions.
I’m just not familiar with the Senville brand..I’d go with LG, Mitsubishi, Sanyo...those are probably the most widely used brands. All will have the equivalent of the Senville units. Support on those brands will be superior, and support can be critical when operating problems arise.
Of course they will probably be 20% more expensive.
Mitsubishi is double the cost. LG is about 20% more expensive as you say. I didn’t encounter Sanyo when searching for mini-split heat pumps, will have to check them out.