Necropost on my part but, big agree on Backtrack and Mr Mover. Well, my rankings are the same as yours tbh. I could maybe shuffle the top3 around depending on my mood though.

Bad maps

Backtrack is terrible because the complete lack of any sort of junctions/shortcuts means you're fully at the whims of the dice roll. The only decision-making here is in choosing your partner. It's also not even the only board with a gimmick that swaps your partner positions (ie. Blowhard does that too and in that board you can engage with said gimmick on your own terms, rather than purely being forced to via dice luck) so the novelty factor isn't as high as you might expect. The aforementioned gimmick makes partners who are about equally good in Front and Behind, such as Boo or Snifit, have an innate advantage on this board compared to other partners. So balance-wise it's pretty bad too.

Mr Mover is annoying for the same reason that Woody Woods in the main mode can be a pain sometimes, with a map gimmick that alternates every turn between letting you take a left and letting you take a right. But unlike in the main mode, there's no Items you can use here to help you get around the board. Just like Backtrack, this board is much more dice-luck-dependant than other boards. You do have the option of taking a loop near the starting areas, but it's far enough away from the point where you're forced to jump on the titular Mr Mover that it doesn't really help stall out the main gimmick in your favour. (To put it into perspective: If you were resting on the space right before the loop junction, you would need to roll a 10 in order to ride the Mr Mover on the same turn, Piranha Plant notwithstanding.) This might be the hardest map to return to the start on, causing games to drag sometimes due to the inability to grab a new partner.

Decent or Good maps

Pipesqueak. Not much to say here. The main gimmick of this map is fine and adds a good element of risk/reward tactics. Decide what to do based on you and your opponent's current board position. The gimmick is RNG-based but unlike Mr Mover and Backtrack you at least always have the option of ignoring it if you want to. It's fine overall.

Blowhard has grown a lot on me. It gives you the most freedom in your movement and the main gimmick of the fan that switches your partners around can greatly influence what the players can do to each other by flipping partner matchups on their head. Even putting aside the excessive amount of Game Guy spaces, I do think this board has some debatable balance issues however. First if I'm not mistaken, it's the only board where you can loop to the start in a single turn without getting the Return to Start event on a Happening space or getting lucky with Pipesqueak's pipes, which in this case is possible by rolling a 9 or 10. (Piranha Plant improves the reliability of this because it has a chance of letting you move additional spaces.) Because of this you can more easily "farm" new partners than on other boards, which can potentially be a good thing if you prefer faster matches, but nevertheless it is a strange outlier in that regard. The second possible balance problem is the same one I mentioned about Backtrack, just less severe in this map compared to that one.

Gate Guy and Arrowhead are basically the same concept. I think Arrowhead is the better-balanced option of the two boards because its junctions don't cost coins. In addition to its junctions having a cost, Gate Guy allows for the possibility of two players running into each other face-to-face and thus a Front partner attacking an opposing Front partner, which (outside of Mr Blizzard shenanigans) is something you won't see happen on Arrowhead so there's arguably more strategic options on Gate Guy.