It's a given that every Democratic candidate will be antigun, to a greater or lesser degree. They have to play to their base, to have any hope of getting the nomination. (It pains me to say this.) However, the degree of difference among the candidates could become significant. For example, they all say they want to "ban" "assault weapons." Whether that includes grandfathering of existing weapons could be key. Given the huge number already out there, a "ban" with grandfathering could be meaningless. In fact, owners with the foresight to stockpile them could profit handsomely.
If all "Mayor Pete" is proposing is background checks and a prohibition on guns for mentally incompetent Social Security recipients, that would make him one of the milder Dem candidates in regard to guns.
I've been saying that you're going to hear a lot of antigun rhetoric from Democratic candidates in the nomination phase of the contest, but they will turn strangely silent when it comes to the general election. The reason is that they have to carry the Rust Belt states of Pennsylvania, Michigan, and Wisconsin, and/or the Sun Belt states of Florida and Arizona, and there are a lot of gun owners in those states that the Democrats dare not alienate.