Sal-GQ's comments

It would be "fewer than 10 people" because the word "people" is quantifiable (each person can be counted individually). You can't have 9 and a half people so you would say "fewer than 10" which would mean any number between 0 - 9 people.
It's different with nouns like "time" and "money" because they can have increments in-between the stated measurements.
e.g. If you were to say "FEWER than 10 minutes", you're referring to a specific number of minutes up to the 9th minute exactly, whereas "LESS than 10 minutes" can mean any amount of time up to a fraction of a second before 10 minutes, such as 9 minutes and 59 seconds. more »

"much", "far" and "a lot" can precede both "less" and "more.
e.g. "there are far more cars on the road now than there used to be"
"I definitely like chocolate a lot more than sweets"
"I I feel much more prepared this time". more »