So, after doing some research, we decided to go with the KTuner. Bought from Two Step Performance for $449, and, for that price, they include a custom tune (normally $79) that should be good for about 219 HP/258 LB-FT in the wife's car. Those numbers are up from the 187 HP/200 LB-FT that Two Step Performance dyno'd a Civic 1.5T 6MT at, before any mods.
The dyno results of the factory, non-modified Civic 1.5T at 187 HP/200 LB-FT indicates something interesting - Honda is quite conservative with the HP/torque ratings of this car, since it's rated by them at 174 HP/167 LB-FT. This was also shown by Motor Trend in their testing back when the Civic 1.5T came out in 2016...
So, about 32 HP and 58 LB/FT increase, at the wheels. Not bad for $449! That's without any other mods. I've decided not to add an intake, exhaust, or any other performance bolt-ons, at this time, since the gains for those items seem to be minimal.
There are lots of tweaks and adjustments you can make with the KTuner, including elimination of rev hang, "quick turbo spool", etc. And you can switch between up to 3 different tunes on-the-fly, using the cruise control buttons.
This mod should make the wife's Civic faster than quite a few hot hatch-class cars out there, including the stock Civic Si, VW GTI, and maybe even the stock WRX, since, I believe this is a lighter car than the WRX. (Honda lists the curb weight of the 2018 Civic Hatchback 1.5T 6MT as 2822 lbs, and Subaru lists the curb weight of the 2020 WRX as being at least 3294 lbs)
Can't wait to get it and plug it in!
I think I'll start running M1-ESP 5W-30 now. Sucks that I'd just changed the oil (been using the VME and M1-AP that I bought over 50 quarts of last year for $2/qt during the AZ clearance). Read here where it's on sale at NAPA now for $6.99/qt when you buy 5 quarts, and then there's a $10 MIR (gift card).