Yes you can if the base has the same diameter
Not enough information to answer this question! What is the wattage rating of the fixture? What type of bulb are you referring to?, 75 watt equivalent CFL, LED or 75 watt incandescent? If you're referring to 75 watt equivalent spiral CFL bulbs, then yes. The most common fixture rating would be 60 watts per socket for incandescent bulbs. CFL bulbs draw much less power so a 75 watt equivalent bulb would safely/easily work.
Bright and a saving
I only used them indoors.
The same as a regular light bulb!
As these draw 14 watts each, the total load would be 42 watts so they should work fine with 18 watts left over. These do get hot however. Most of my fixtures are open except an enclosed porch light which seems to be doing fine.
I would select the bulb based on the lighting effect I wanted. A color temperature around 5000 degrees Kelvin (Daylight color) would display more like a sunny day. I personally like a lower color temperature on plants since it produces (in my view) a more subdued or less harsh appearance.
Believe they only come in medium base but by all means check on the internet.
The diameter is 2 inches and the total height is 5 1/2 inches.