I wasnt questioning whether they belong. Questioning how meaningful season point differential is with the different quality of wins.
Interesting question. The answer IMO is that there is no answer. It is entirely case by case.
For a team like KC it is pretty important. They have been pretty much the same team all year long. We can look over the course of their 17 real games and get a very good feel for them. This is a good thing as it gives us a chance to look at their entire body of work and make judgements on them, their 16-1 record, their point differential, their SOS and everything else. The only big issue between this team and the one that will play at the super bowl is they will be without Fisher, so we need to take that into account. They may or may not have Watkins, but frankly he is an after thought in your offense. A nice little bonus but he doesn't move the needle in a meaningful way.
So what I believe about KC. Their 14-1 record of the context of 128 point differential matters (I'm entirely taking out week 17). So let's extrapolate it out and assuming the same differential call them a team that would be 15-1 with a 137 point differential.
The Only teams that have gone 15-1 or better before.
SF in 84 with a 248 diff, Won SB
CHI in 85 with a 258 diff, Won SB
MIN in 98 with a 260 diff, Lost CCG in OT
Pitt in 04 with a 121 diff, Lost CCG 41-27 after being down 24-3, 31-10 and 41-20 that game.
Pats in 07 with a 315 diff, Lost SB
Packers in 11 with a 201 diff, Lost Div to SB champ Giants 37-20 after 4 turnovers.
Panthers in 15 with a 201 diff, Lost SB
There aren't exactly a lot of data points here, but 137 is certainly on the low side for such a record. The only team comparable to them is Pitt in 04 point differential wise. As far as KC opponents, they gave exactly as many points as they scored on the season give or take 1 or 2. It wasn't all that hard a schedule. It was almost perfectly average. And the fact they only managed this point differential against it is a statistical oddity.
It has been floated out they often coasted with the lead. I believe that is partly true. Even if it is, that certainly isn't a good thing that they often let games become 1 score contest that they had to win walking a tight rope late. While it's better that having to scratch out wins due to lack of ability, it isn't a great deal better either. It's a bad habit that they were lucky didn't bite them more of true.
However, that wasn't always the case. They were down late week 2 and weren't coasting. In week 9 they gave the ball back to the Panthers late with a chance to tie or (unlikely admittedly) win. They were down late vs the Raiders in week 11 and needed a score in the final 2 minutes. Denver had the ball 3 times in the 4th with a chance to pull ahead in week 13, In week 16 the Falcons were up in the 4th and when down had a chance to win on their final drive. It wasn't just a case of a superior team smooth sailing. They had to struggle to win many of their games.
Does this mean I think they suck? No. Does it mean I think they were fortunate? A little. Luck is something you create with good habits, but it also just kind of happens sometimes. In reality i don't believe KC is as good as their record says, but they still may be the best team in the NFL.
As for the Bucs, you can't really dive this deep on them. They have been a work in progress all year that as been improving and will probably still not be where they wish they would be come tomorrow. But that's okay. I don't buy the narrative they need their game of the year to beat KC cause they are just so much better. Just like I don't buy KC needs their best game of the year to beat the super talented Bucs. Neither of these teams in my estimation is much if at all better than the other at this point.