A 60W bulb has an output of ~800 lumens and a 100W has the approx output of ~1000 to 1100 lumens.

You should not put a 100W incandescent in a socket intended for a 60W even though the light "seems to work".

As for whether a CFL or LED bulb can be used, that depends more on the physical dimensions of the bulb and the space available under the lamp shade.

Looks may also play a part as some people don't like the looks of a CFL or the light output color.

In any case, both CFL and LED lights consume less power and there's no reason why they cannot be substituted for an incandescent from the looks and physical dimensions.

A word of caution, some manufacturers of CFLs and LEDs could be somewhat deceptive in claiming "output equivalent to XX watts" and not actually stating the actual light output.

The fixture restrictions have to do with electrical current limits, overheating, fire safety, all sorts of things that it's not a good idea to push your luck with - but those are hazards of incandescents, not CFLs or LEDs. When the pendant says it takes an incandescent bulb, that means that it's a "normal" screw-base as opposed to a fancy pin-base that requires a fluorescent or halogen or some particular thing.

If you want more light than a 60W incandescent will give you, using a screwbase 23W CFL ("100-W equivelent") is perfectly fine, but I wouldn't use a 100W incandescent bulb. Try a couple of different CFL wattages and colors (2700K if you like incandescents, 3100K if you like halogens) until you find one you like.

Here is a link that might be useful: CFL watt equivalents that may or may not be accurate in practice

Personally, I would get a pendant that is at least 100 watts. As already mentioned here, you cannot for safety reasons put a 100 watt incandescent bulb into a 60 watt fixture. I have a 100 watt rated can light over my sink. I always put a 100 watt flood lamp in it. I like it bright & quite often, it's the only light I'll turn on in the kitchen. I'm considering replacing it with a hanging pendant with 3 shades/pendants. To sum it up, go for more wattage. If it's too bright, you can always put a lower wattage bulb in, but it's difficult to go up. The CFL's do work, but have to warm up to come up to full light power. Hope this helps.

The wattage limitation is on light fixture mostly because excess heat from an over wattage bulb could build up and damage the fixture as well as cause a fire. The limit should be followed for incandescant bulbs. Because CFL and LED bulbs convert less electricity to heat and more to light a so-called 100 watt equivalent bulb of those designs could be used in your fixture.