Since people on social media can follow unknown users and most personal accounts on Instagram are private, you cannot check their photos.
So you have no choice other than their profile photos and the right to know whether the follower is worth accepting.
And also, you may not take a risk and accept their request and regret it after viewing their Instagram photos.
In this case, it is better to check the Instagram profile photo for a private account, and there is no difference between private and public accounts; through the methods above, you can view the Instagram profile picture of either private or shared accounts.