In an interview, how can I ask the question (without significant
negative effects on how the interviewer views me)
"Do you restrict and monitor internet access of your employees, and if
so, in which ways?"
It's certainly reasonable to ask "Tell me about this company's Acceptable Use policy?" That is basically a non-confrontational way to get much of the information you are seeking. At least for me as a hiring manager, there would be no negative effects. I can't speak for all other hiring managers, but in my network of friends, none of them would hold that against you either.
That starts the conversation, and you can judge for yourself where you want to take it. You might want to probe deeper and ask specific questions about restrictions, monitoring, etc. Or you might sense that this line of questions isn't well received, in which case you can graciously back off.
As @bethlakshmi correctly points out, not every manager will have a lot of details on hand about how employee internet use monitoring is done. In my experience, there is usually a written policy. That may not have lots of details, but often gives you the broad warnings about what the company expects, and what they may choose to do.
If challenged and if you are feeling nervous, you can always follow up with something along the lines of "I like to do some work from home after hours. I'm basically wondering if I can use my own computer to access the corporate network, or if I'll be required to use a company-provided computer?"