I know this is pretty late. Even though no one's probably gonna read this, here are my thoughts! I did all songs for rounds 5-8.
-Ballade v King Knight-
Dewey Newt - 100% Epic. This arrangement uses the themes in a way I never would have thought of. The parts are well used and wow does it sound good. The last part especially sounds really good. Not much to say other than well done.
Gario - I love how the atmosphere is immediatly set here. The synths are well used, although the lead is a bit jarring when it first comes in. There's a lot more of the sad sound of Ballade than the epicness of King Knight, and yet both are very clear. Very well-arranged. It seems just a bit repetitive, but not really enough to bother me. The robot sounds were really good too, along with that beginning arp they set the mood of the piece very nicely.
-Uranus v Wandering Travelers-
JohnStacy - FIESTA! The themes here are so well integrated it's crazy. The arrangement is really good, and I love that piano part and the big brass parts. I like some of the reharmonization, it gives the piece a really nice, jazzy vibe to it.
Chiwalker - The themes weren't very recognizeable at first, but as soon as the arp came it with the power saw lead, the arrangement seems to fall more into place. It's a bit simplistic at times, but overall this is a very nice dance take on the two themes.
-Saturn v Polar Knight-
TheShaggyFreak - There is a lot of dissonance here, although a lot of that is due to the original composition of Polar Knight. I like the intro here, it's one of the best parts for me. It may be just me, but I feel like there's a part missing for most of the song. Although, it's a very somber take on the themes which is very unexpected, so props for creativity.
-Enker v Specter Knight-
PlanarianHugger - Pretty good integration of the themes, although sometimes a few things sound slightly off-key, probably problems with the chords not matching at times. The melodies seem to work well together for the most part, and there are some really good parts here, like when the arp part takes the lead, and the harmonization of the melody soon after. Sometimes the switching of leads is a bit jarring, and not each part transitions very smoothly, but there's a lot of variation and a lot of it is pretty good arrangement wise.
Starphoenix - There are a lot of really cool sounds here, and each part transitions well, but I can't get a grasp on the key. It seems like it would be a really good arrangement if each part was kept in the same key as the others. More than half of the song seems to have parts that clash with each other and although this does start to get a bit better as the song goes on, it repeats the intro which was more jarringly off-key than any other part of the song, so even with the cool glitchy outro, the end just sounds weird and unresolved. If the key was the same across all parts I'm sure this would be a really good entry.
-Pluto v Shield Knight-
GCJ - Too much 80s. What were you thinking?
-Punk v Mole Knight-
Xenonetix - I like the piano arrangement idea and it's done really well here. Maybe it's just me, but I hear a lot more of Mole Knight than I do of Punk, but the themes are integrated well and flow together nicely. I don't know if it's just reverb, but it sounds like the pedal is down the whole time and is never brought up to make sure notes don't last into the next chord if they don't mesh well. This isn't a problem for most of the arrangement, but when the left hand part is doing the super fast arp-sounding part, it's a bit messy. That ending slow-down part sounds really nice though.
-Mercury v Propeller-
Thirdkoopa - The parts were confusing. I couldn't tell if they were in different keys for half of it, or where the beat was, and the arrangement seems kind of all over the place. I'm not really sure where each piece was played, although I could hear the lead from Mercury playing very quietly at the background at one point which sounded nice.
-Venus v Shovel Knight-
Jorito - I love the integration of the themes here. Even if most of the background is just chords, the melodies are mixed so well and I love the instrumentation. I don't know what that sound is at 3:08, but it just sets such a nice atmosphere. This arrangement is really good and gets better as the song goes on. Also those lyrics are pretty good.
Megadrive - A good dance beat. I like the arrangement here, these melodies flow pretty nicely together. Also I really like those bell sounds. A little more variation in the bass and drums would have been nice, since the bass playing almost the same rhythm the entire time, and the drums only seem to vary in whether the snare is playing or not, even if there are a few tom rolls that keep it from getting too stale.
Chiwalker Knight v Mars - These songs fit really well into a dance song! It's not always very complex arrangement-wise, but I like the use of the arp during the less complex parts, and when it builds up with all the different parts it gets really good.
Xenonetix Knight v Saturn - A bit on the repetitive side, but delicious and groovy.
That was pretty long. Anyways, lots of good entries! Very fun and enjoyable to listen to all of them.