For me, the top 3 fun and easier vertical shmups are:
Rayforce
Batsugun Special Version
Battle Garegga Type 2
All have great music, graphics and gameplay and can be quarter fed all the way through.
Garegga has an adaptive difficulty that lowers with every death and Type 2 can be less frustrating than vanilla because the enemy bullets are easier to see.
Batsugun Special Version is easier than the original version in several ways, especially the smaller ship hitbox, which makes it really fun for me.
Not sure what rom versions are in the list, though.