The reality is that even the earliest 200-series are incredible performers and honestly doesn't give up much to the latest model years. But here's some detail that may help you decide where you want to be.
The major breakpoint as others pointed out is the '16+. That includes a major interior and exterior refresh for both LX and LCs. Along with major changes like 8-speed (up from 6, much lower 1st gear and crawl ratio), bigger brakes, and a host of detail feature enhancements to LC and LX. More trickle down items to the LC, but the LX also gained goodies.
There is a more minor breakpoint in 2013 where both models got a minor exterior refresh. Functional changes with the addition of MTS, turn assist, and incrementally better traction aids. Some trickle down features to LC, and LX gaining features.
2020 got special trims in the Heritage Edition for the LC, and Sport Edition for the LX. With the availability of 2-row trims, in the HE, and LX as a lower trim option.
Another way to look at this is to find specific features to see if the specific LC or LX example you're looking has it. This list is focused more on the potential differences between LC to LX, but could be helpful to know what later model years got as features.
1) More sound deadening (acoustic glass, engine covers, more extensive interior insulation)
2) Powered rear hatch for open/close, also key fob operated (later LCs got this)
3) Soft open rear lower tailgate, with power latching
4) Surround camera system
5) Ventilated/Heated front row (later LCs got this)
6) Mark Levinson Reference (only other model to get the Reference system is the LS) w/surround (19 speakers vs 14, 10" sub vs 8")
7) Power side view mirrors with auto-fold (later LCs got this)
8) AHC - AVS, lift on demand, adjustable and continuous damping logic, anti-dive/roll/squat, leveling, etc.
9) AHC underbody armor
10) Shorter roof rack (LC has a longer roof rack with 3 supports per side)
11) Steering headlights (AFS)
12) Projector headlights ('16+ LCs got this)
13) Headlight washers
14) Storage in rear seat armrest
15) Power slide rear seats
16) Second row storage on front seatbacks is a panel vs net
17) 14-way adjustable driver seat vs 10-way LC (passenger 12-way vs 8-way)
18) Adjustable tilt front headrests
19) Power stowage for 3rd row seat
20) All windows down by holding remote door open button for 3+ seconds (not sure Toyota's have this?)
21) Substantial Lexus key fob
22) Fade-To-Off interior lighting (I believe LC got this in 2014?)
23) Puddle and side step lights
24) Door sill lighting
25) Interior ambient lighting
26) Additional trunk side light and open tailgate lighting
27) +2hp / +2tq (requires 91 octane, LC is 87 octane)
28) Semi-aniline leather and more luxurious interior appointments
29) Ventilated outboard rear seats
30) Four-zone climate concierge
31) LED Headlamp with AHS Sequential Turn
32) LED Cornering Lamp
33) 12.3-inch high-res split-screen display (LC 9")
34) Head-up display
35) Steering wheel paddle shifter
36) Door puddle projector lamps
37) Rear door retractable sun shades
38) 2020 gets special trims: "LX570 Sport" to "LC Heritage"
39) Dual screen rear entertainment
40) All-Speed Dynamic Radar Cruise Control (LC DRCC for 25mph and up)
