You lube mostly to silence the switch, makes the switch feel a bit smoother BUT it's not a band-aid for a bad switch.
Lubing your Cherry MX Browns will make them smoother and help greatly with clatter, not make them feel like Gaterons, the scratchiness in Cherry switches is in the sliders.
Also the way to lube them depends on the type of switch. Topre you lube only the slider and housing. Cherry MX you can lube the housing, spring, and slider (same for any thing cherry-like, Gaterons or Kalihs), same for ALPS switches too.
just makes is smoother and some would argue lighter
definitely changes the feel
If the switches aren't lubed good, then lube will make the switches feel a tad lighter.
Made my 45 gram Topres feel 50 grams to 45 grams when I lubed them.