You didn’t mention what type of listing you have (whole home, shared space, etc.). I think if I had a shared space listing, I would make everything much more strict, but with my whole home listing, this is what I did:
Instant book: Yes. The ranking boost is a big deal. I don’t think I would ever turn it off, but if I did, I’d have to be very confident in maintaining a healthy occupancy rate before doing so. One caveat is that I combined instant-book with a minimum advance notice of 2 days.
Profile Photo: No. About 1/3 of my guests had profile photos of that didn’t include the guest’s face in the photo (i.e. it was a photo of their pet, or their children, a flower, etc.). It’s not worth a lot, but I agree with @JJD that, for the most part, it shows the guest made an effort of being cooperative. Still, I didn’t turn this on because I don’t care what guests look like.
Pre-booking message: No. I didn’t really need to know anything about the guest group that wasn’t in the reservation details.
Recommendations from other hosts: No, then yes. What I decided was to turn this off when I was new and turn it on after I’d been hosting a year. The reason is that turning it on not only excludes guests with bad reviews, but it also excludes guest with no reviews (i.e. 1st-time guests and guests that have completed reservations but the host never left a review). Guests with no reviews were easily over 50% of my business for the first year and 70% the first 6 months.
Government ID: Yes. I verified my own ID as a host and I expected it of guests. I think it does prevent some bad guests from booking, but there’s way to no measure it. I’ve read it’s possible to fake and it’s also far from a guarantee that a guest isn’t planning to do something “bad”, like have wild party, smoke in the house, etc. but for the most part, it shows the guest’s effort to be “good”.
Cancellation Policy: I don’t think you can make the best decision on this until you’ve been hosting for a couple years and you have data on how far in advance guests book and how close to check-in guests cancel (even then, any data from March 2020 through at least July 2021 is skewed). I only used flexible policy. My data showed me that using moderate policy would never have been a benefit to me (because I never had a cancellation less than 5 days before check-in). On the other hand, there is a specific search filter for flexible, so using a flexible policy might help. [Edit: as JJD said in a later post, the search filter actually includes flexible and moderate, but not strict.]
Also, regarding “people looking to take advantage,” Airbnb is trying to stop some bad behavior by using an algorithm to detect a guest’s intent to have a party at your listing. Here’s one thread on the subject, but there are others. It’s another imperfect solution, but something hosts should be aware of.