The SNES is a rather robust machine; however, there are still fragile components inside. There are a few things to check for: 1) Check to see if you are actually drawing power from the AC adapter. Cheap, 3rd-party adapters are not noted for their longevity, and the original Nintendo ones are quite ancient now as well. 2) Check the power input jack on the SNES. There should be a pair of metal teeth inside a plastic circular enclosure. If that enclosure is broken, it may not be making good contact with your AC adapter. 3) The fuse that is in the SNES is notorious for breaking. Every time I get a new SNES in, I'll replace the picofuse with a compatible (125V, 1.5A) resettable polyfuse. Basically, if there is a power surge that blows the fuse, all I'll need to do is turn the SNES off and then on again to reset the fuse, instead of having to replace the fuse.
You can actually install High Sierra on an SSD without automatically converting to APFS, using, of course, HFS+ instead. 1) Download the MacOS High Sierra installer from the App Store as usual, making sure it’s within the /Applications/ directory. You will need the full installer to have the Contents/Resources/ options available to you. 2) Open the Terminal application, found in /Applications/Utilities/ (or from the Utilities screen menu options if booted from a USB boot installer) 3) Enter the following command syntax at the command line prompt: /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO 4) Hit return key to start the macOS High Sierra install process with the –converttoapfs NO directive, thereby skipping the APFS conversion of existing file system
This is because one of your PPU chips (picture processing unit) is failing, specifically, the PPU2 chip. The PPU1 generates background character data, rotation, and scaling, while the PPU2 performs special effects, like the spinning Arwing in the background of your StarFox game. If you can repair or replace that chip, your problem should go away.
Unfortunately, Nintendo cheaped out when it came to the VB. The ribbon cables that connect the motherboard to the display LED board isn't soldered; they're GLUED. So even with old new stock VBs, the glue will degrade and relax the pressure, losing connectivity. It is possible, though not for the faint of heart, to open the VB, remove the glue, scrape away a bit of the ribbon cable to reveal the metal traces, and solder those traces to the LED board. This is a permanent fix, too - unless you screwed something up, you'll never have to worry about the display glitching again...well, for connectivity issues.