Nice, now your guide is complete. <3

HAH I found the other one as well.
"Yarr! Starboard at once!" is being unlocked by picking "No Fail" mode and then playing a map but you only press the notes on the right circle. I had the idea because the achievement icon showed an eyepatch and starboard is refering to the "right side" when sailing. Completing a map (i picked the last one from pack 1 again) awarded me the achievement.

I just unlocked "This game can look better..." by lowering the quality as much as possible.
I don't know how many of these are needed but what I set up was this:

Gameplay:
Show FPS: Off
Special Section Effects: Off
FPS Limit: 30
Swap Combo and Accuracy UI: Off
Playfield Scale: 0.4
Enable Judgement Bar: Off

Audio:
Mute Hitsounds: On
Hold Release Hitsounds: Off
Mute in Backround: On

Graphics:
Resolution: 640x480 (this should be shown ingame by default in current version despite the playing having a higher resolution, don't change it, it might be bugged right now)
Fullscreen Mode: Fullscreen
The rest: Everything turned Off and Bloom Effect to the lowest of 0.3

Input:
No changes needed here.

Then I played a map (I picked the last of the first pack because its short) and after completing it, I received the achievement.