The better solution to dry winter air is to tighten the house up to the point where it stays above 30% RH in winter, and use mechanical ventialation (particularly exhuast fans in bathrooms and kitchens) to expell any concentrations of indoor air humidity/pollution. If it's so tight that it stays above 40% RH all winter (difficult to achieve with retrofit air-sealing in most homes in 6000+ heating degree-day climates) heat recovery ventilation (HRV or ERV) under dehumidistat control, or continous low cfm exhuast ventilation in bathrooms/kitchens would be in order. If the air isn't leaking through wall cavites or ceiling leaks, it isn't creating localized condensation and long-term accumulation of humidity on the exit paths. (Vapor barriers & vapor retarders seem to have captured the popular imagination, but most condensating/mold related moisture problems in buildings are from air leaks, not vapor permeation through walls.)
The most important places to concentrate the effort are the basement and the attic, to quell the stack effect. Air leaks in between are subject to the wind, but the stack-effect works 24/7, creating suctino pressures to the tune of ~4 pascals for every 10' of height. Stopping the inflow at the bottom, and the outflow a the top are key. Besides the obvious window & door weatherstripping, dryer vents, flue dampers, etc, foam-sealing the foundation sill and band joist is usually the single largest overlooked air leak in most homes (it's typically bigger than an entire home's worth of window & door weatherstipping). Attic hatch weather stripping, while important, is usually a fraction of the air leakage from recessed lights, plumbing & electrical penetrations (particularly plumbing chases where vent stack follow through to the roof), flue & chimney chases (use sheet metal air dams), and any balloon-framing/partition wall framing with leaky or absent top plates. Fixing the bigger air leaks are typically easiest, an provide the most benefit. After fixing the obvious, it often takes pressurizing/depressurizing the house with windo fans (or calibrated blower doors) to find & fix the myriad smaller leaks.
After any round of air-sealing, check for backdraft potential on any atmospheric-drafted combustion equipment.
As for the original question, with a gas-fired burner the cold end of the heat exchanger has to stay- under ~90F on the fire/exhaust-gas side to get 95% combustion efficiency. Assuming 65F air on the return plenum that's not too tough to do as long as the air flow stays high enough. With a 25-40F delta-T on the heat exchanger it means the exit air will usually be well-under 130F, often under 115F. With an 80% system it doesn't much matter- you can run the thing in "scorched-air" mode and it can still hit low-80s for raw combustion efficiency. Running it hotter there's a bigger delta-T between the air & fire sides, and the heat exchangers can be more compact too. Many 80% furnaces control the blower with snap-disc type thermostats on the heat exchanger to guarantee a minimum average exhuast temp to prevent condensation damage to the heat exchanger, whereas 95% furnace controls need to set a max temp to maximize condensation, and minimize exhaust temp to well below the operational range of plastic vent pipe.
Duct design affects the total air flow, and will affect exit temps. A 2-stage 95% burner with a 2-speed (or variable speed) fan can still deliver warmer air at the register than a bang-bang controlled single-speed high-flow 80% unit- it depends on both the furnace and the duct design. Anying above 110F is usually pretty comfortable, but under 100F (body temperature) the wind-chill temp at the register becomes relevant. (Low speed air can still feel pretty cozy even at 85F, but would have a chilling effect at most air-handlers' high-settings.) 95% 2-stage units are counting on running at low-temp low-fire low-speed most of the time to achieve that AFUE.