For ages, my go-to combination about 10 years ago was rF1's Lotus 23b by st-Dave at any smaller tracks, especially Brands Hatch 1950, Putnam Park etc. I wish someone makes this car into AC, with similar kind of physics. Have to confess, I converted it to AMS1 for personal use, and it's awesome in there as well. But with different throttle map code in AMS it's even more momentum car than it was in rf1, and its the rare occasion where i miss that immidiate low-end torque that rf1's version was giving. (while still the car being pretty low-powered). The brilliance of that Lotus is it's very stable, very low and light, that makes it corner amazing, but unlike more modern cars of similar class, it is still having that old-school suspension travel, a bit of rolling, it's tailhappy if you really force it into that, but its power is not capable to spin you around, the engine bogs down at exact right moment of a slide, and this alone feels like a cherry on the cake.
HistorX's Pantera felt amazing at Zandvoort in rf1.
In AMS the HistorX Porsche 911S 2.0 feels utterly amazing at Oulton Park.
Also in AMS the Opala at Buskerud Ice is a proper challenge and workout, providing a huge grin in the face.
in rF2 I've had a huge blast with Enduracers Alpinie A450 @ Zandvoort, then MCR at VIR full, F-Vee at VIR North, and AJR at Ibarra.
in AC currently the best combo for me is Legends Cars at Bikernieki - any layout, probably High Speed layout the most, for most authentic and even scary experience. Also same cars and Russell-Alexis at Sergio's Ring Djursland and LilSki Calabogie.