Greasy Fork

Is a value greater than 100 possible? How does it display more than 100 at a time?

Yes it is.

You can write any number of you choice, like 999999999, but from what I've seen google only shows 200 results, so there's no real point in writing a number bigger than 200, plus the fact that 200 is already a very high number, and because it's a high number google may ask you to complete their recaptcha thinking you're a bot if you do a lot of searches simultaneously. I personally use the number 200, and I just have to complete google's recaptcha once a day or less depending on how much (and in what the time span) I use google during the day...

Google displays 200 results the same way 100 results are shown, there's no real difference in how the result page looks like.