https://www.loadcalc.net/
Yes a load cal would be great. Above one is free. There are many room by room load calculation online for a minimum fee also.
Yes a uncomplicated basic 80% furnace in your area would be the way to go if your considering a gas system.
Prestige in a brand ( you mentioning York lack off ) does not mean nothing IMO, there are many brands you probably never heard of out there, does not mean they are inferior units just because they are not so recognized. I think there are only around 5 ( give or take ) recognized major manufacturers that make all those lesser recognized brands.
Being in California registration of equipment is not required to receive the maximum manufacturers warranty. The other location is Quebec. All other areas need registration. I’m not 100% sure but I believe all new equipment installed in California needs to be a matched system.