i had a ps5 and now have a ps5 pro. You just have to set display to 4K 120hz in the PS5 system menu, turn on the appropriate setting on your TV HDMI port (LGs would be gaming mode, VRR on, no post processing, deep HDR enabled) and it generally just works.
Most games have a quality (30 fps, 4K) or performance (60 fps, 1440p usually) mode. With PS5 Pro you might see a blend third graphics mode which is usually 4K 60 fps, if its not there you are still kinda stuck then choosing 30 or 60 fps mode.
The really big option is PSSR, which is Sony's version of Nvidia DLSS. PS5 Pro has a specific chip for it and games that let you turn it on have way better raytracing. There are very few games unfortunately that have a PSSR mode.
Ideally if you have an LG OLED TV plus pro you hope the game supports 60 fps, 4K, PSSR running at 40 fps VRR. That sync's perfectly with panels 120hz displays (120/40=3 ticks per frame, no added latency and no screen tearing). Without VRR you'd either have to get some input latency with forced v-sync or screen tearing without v-sync.