I ultimately decided to use an entirely-stock Alfa Romeo MiTo for the European Sunday Cup 400, driving on Comfort Softs. Then I did the Lightweight K Cup in a Honda Beat, specifically one that had a widebody and was on Comfort Softs. I took third for that race at Tokyo South, even though I had already cleared it previously. In hindsight, I think I could've switched to Comfort Hards and jacked up the power, seeing how a lot of this layout either has straights or higher-speed corners.
Next, I plan to use a widebody Ferrari 458 Italia for the Ferrari Circuit Challenge, and it comes in at just below the 700 PP limit on Sport Softs! I'm not entirely sure of what particular GT-R I'll ultimately use for the GT-R Cup, though I did have a relatively trusty GT-R Nismo '17. Even if this particular car doesn't have the Chiron engine, I've still tuned it quite a bit. Sure, I could use the R34 I had swapped an R92CP engine into, but it'd likely cost me a notable amount of credits to fully-tune it.
While I do also have all the Group C racers, I think I'll still use my Mercedes-Benz Sauber C9 for the Special Event, seeing how I've already bought the other Racing tire compounds for it. I'm even going to tinker with the settings to get it just below 950 PP in particular.