Basically with some "modern era" model train designs anything under 0-36 or 0-42 seems almost like luck. Go as big as you have room to if you might one day have plans of bigger locomotives. In fact, consider mixing in GarGraves or other more squared rail to handle any smaller flanges you may find.
The real deep flanges bottoming on 0-27 was a rare few or some loco, maybe prewar? I had a couple things as a kid that hit some O27 ties.and clipped Super O rail holders so hard you couldn't run them.
Newer wheels have a fast angle vs flat tread; and with that, smaller flanges that ever it seems, that perform the same or better really.
As far as that loco goes, most new have an "advertised minimum curve" if you search out the documentation on Lionels site it's usually there as an searchable ad/catalogged styled page and/or in the manual.
But keep in mind even the postwar Berk couldn't pull off O-27 curves and some old diesel rollers on long roller arms will drop off the center rail on O27 curves as well.
Coupler variances in size over the years means occasionally some bind happen on 0-27, 0-32.
Nicer scale locos tend to need a min. starting in the 50s.
How is the loco not making the turnout? Does it hit something? Does it derail from too tight a curve? Or is it electrical shut down?
The electrical timing of rollers moving across the turnout rails is never perfect for ever type of switch, car, or loco. Adding a tether from loco to tender roller is the best fix usually making it a very "universal engine" from then on in. Other times a roller swap will work well.
O gauge 022 turnouts are one of the smoothest.
Less prototypical looks wise, and point operation wise, very basic so needing home spun ant derail, Marx prewar are the smoothest turnouts because there are no frogs, diamonds, big gaps or guides rails.