I would say the heat have some individually pretty great defenders. Bam, Butler, Iggy, Crowder are all above average to near elite options. They also mix in some no so great defenders however. Guys like Hero, Robinson, Olynyk, Dragic all try on that end but can be taken advantage of either by bigger, or quicker players. And those guys kind of have to play because they bring a lot of offense.
Against the bucks who don't have a ton of individual great shot creators (Middleton is really the only one) it can be hard to truly take advantage of those weaker defenders, the C's I think can. Even without Hayward (i imagine he misses the start of the series, maybe returns by the end?) the C's will likely have a miss match somewhere on he floor they can exploit. One of Tatum/Brown/Kemba will likely be covered by one weaker defender they can attack.
And while BAM is a great defender his value is really more in versatility then straight up rim protection, MIA probably has less overall rim protection than either PHI (embiid) or TOR (Serge, Gasol).
On the plus side (for MIA) they have about as good a Tatum match up in Butler as you can get. So he will have to work at the very least.