Tires are a pretty personal choice. Nothing wrong with KO2s and they've been arguably a benchmark tire.
That said, there's a number of reasons I've picked other tires, for overall broader capability (without giving up any offroad performance). Additional priorities that I have for a great AT tire include on-road handling and NVH, rain and wet weather, and winter / snow performance. That's where the new bread from my research makes large strides. If I were wanting a tire on the more aggressive end of the AT tire spectrum, I'd lean toward the Falken Wildpeak AT3Ws. Middling to aggressive, Toyo AT3s. There's newer tires still that I haven't had experience with. NTG G2s should be your last choice as they're probably the oldest design of the bunch, pushing 10 yrs now.
Regarding 20" wheels / tires. If I'm being honest, my car is still 95% on-road. Towing on the heavier end. There's stability and handling advantages to running a larger wheel, without as many trades when pushing overall diameter to 34+ inches. Sure, biasing to rock crawler should prioritize 17s or 18s, but there's trades as even my larger 20s with 35s, has enough sidewall that cornering and handling on-road is not as sharp. While offering plenty of sidewall to air down and get busy.
Whatever you prioritize, IMO, wheels and tires are not the place to save money. Where the rubber meats the road so to speak.