For the Ender-3 V3 KE, the bed spacers seem to be 14mm and 16mm. When I look on Amazon, I don’t see any of those heights. I see some packages that have 16mm and 18mm. Will it work if I replace the 14mm spacers with 16mm spacers and the 16mm spacers with 18mm spacers?
it will work, you just need to do the automatic Z offset and automatic bed leveling adjustment.
As long you perform the automatic adjustment, the size of the spacers does not really matter….of course the bed should be - if possible in level.
Might also take a look at the maximal height of the printed objects, it’s 240mm on my printer, with a bed 2mm higher, that value should be reduced to 238mm. I don’t think the printer will know the Z height, i think the bed is the reference for the height.
That value will not matter for someone who will never want to print such big objects.
Also, there is that XYZ control, not adjusting the max height might also cause a light crash if someone would attempt to reach max Z value - i have not tested it, i know however, that the XYZ control does not allow me to crash the nozzle on the bed, there is like 1~2 mm space left between the nozzle and the bed.

