Wherever you buy them, 2 things you should pay attention to: rated lumens and color temperature.
Lumens mean brightness, to put it simply. One "old" 20W bulb has ~300 lumens.
Color temperature is the "tint". Your old bulb had color temp 2700K-3000K. LEDs of that color are called "white", or "warm white" or "soft white". 4000K-4500K is slightly blu-er, and +5000K is bluer yet. Blue-er shades may be called "bright white" or "cool white". I prefer when they publish color temp numbers rather than those ambiguous definitions.
Flat panel is more efficient than "cob" if you need more focused light, ex. for reading or over your work space. It may have then 200 lumens, but all 200 are firing to where you need it, while a 300 lumens "cob" or your old incadesnce bulb would waste some lumens on illuminating the ceiling and walls, and leaving only 200 for a spot that you need. But if you don't need it focused, then cob is fine, though - usually - more expensive than flat board.