Unless yours is an unusually large &/or leaky house, it's unlikely that your actually heat load @ 32F is more than half the output your Payne. IIRC under Title 24 you're only allowed something like 15% (or maybe it's 10% ) oversizing of heating & cooling equipment, which means you're likely to be down-sizing considerably from that Payne. (The heat load of my 2400' 2x4 framed antique bungalow with a lot of R19 ceilings is about 20,000BTU/hr @ +32F.) If the duct design is up to snuff, a pretty good modulating dedicated 1.5 ton single mini-duct cassette unit like the
Mitsubishi SUZ/SEZ KA18NA.th might cut it, since it would deliver ~22KBTU/hr @ 35F (see page 26 for the heating capacity chart.) It's about 3 grand at internet pricing, but can be a DIY project for 95% of what it takes. (The refrigerant charging/commissioning part would have to be done by a pro in CA, but it's only 1-2 hrs of tech time if you did everything else right.)
If gas would be cheaper than mini-splits to operate, as it is in most markets, pellets must be more expensive than gas too(?). I live in one of the most expensive electricity markets in the mainland US, and the operating costs between a mini-split is neck-in-neck with natural gas. And that is at a much lower COP than you would get, due to the much lower temps. (My binned hourly
mean temp in January is about 24F, 8F colder than your 99% bin.)
For a low duty-cycle unit it almost doesn't matter what the service records are between Trane vs. Carrier vs. Goodman vs. brand-X, Y, or Z. Since it's used only as your backup, going with the dumbest least complicated single-stage unit that meets code-min efficiency is would be least risky on overall reliability. With condensing equipment you have a whole new set of venting hoops to jump through to meet code. With a code-min efficiency unit you can probably use the existing chimney, with perhaps a narrowing flue liner. If the narrowing flue liner is required to be stainless, going with a condensing unit would be cheaper, using PVC vent, provided you can find an adequate location for venting it.
If your hot water is also heated with natural gas, you may be better off going with a hydro-air air handler unit operating as loop off condensing hot water heater (or even non-condensing HW heater if set up correctly, and with a big enough burner) , and you're much more likely to be able to match the air-handler output to the actual heat load. With hydro-air you're no longer bound to a particular fuel source- the work just as well with natural gas boilers/hot water heaters, as with wood boilers, etc.
All good decisions around replacement heating solutions starts with the heat load calculation. Without that crucial piece of information it's hard to get to the right equipment decision, and very easy to be led astray. An oversized Trane or Carrier or brand-X isn't worth installing (even as a DIY), no matter what the service reliability records are.