From what I read, I should be able to choose the amount of capital loss carryover I use in 2024, but turbotax uses all of it. Why is this?

The statement that you quoted from Investopedia is not true. There is a fixed set of rules for when capital losses are used and how much is used. You have no choices about it. There is only one way to do it. TurboTax simply follows the rules.

If your 2024 gains exceeded your 2024 losses plus the capital loss carryover, then all of the loss must be used to offset the gains.

Did you actually get that quote from the Investopedia web site, or is it from an AI summary? Is there more than that one sentence, that might explain what it means by choosing when to use the losses?

That is a quote from Investopedia, from this page https://www.investopedia.com/terms/c/capital-loss-carryover.asp#:~:text=Capital%20loss%20carryovers%20provide%20you,capital%20gains%20or%20ordinary%20income.

There is more verbiage, but it still seems to say that you can choose how much to carry over. I could not find anywhere on the  IRS site that clarifies either.

IRS Publication 550 says the following.

"When you figure the amount of any capital loss carryover to the next year, you must take the current year's allowable deduction into account, whether or not you claimed it and whether or not you filed a return for the current year."

Since you have to reduce the capital loss carryover each year by the allowable deduction for that year, "whether or not you claimed it," I think it's clear that you cannot choose when to use the carryover.

I have submitted a request for a correction to Investopedia.