Well, they certainly improves Boho Youyoumu from the first game. Now you can save and heal from the shop, the teleport item are much cheaper, more collectibles to collects (although majority of them involves hidden path, at least I'm genre savvy), and actually we get to fight Touhou character from Youyoumu (PCB). Now I understand why Scarlet Family doesn't have much bosses: 80% of EoSD bosses are members of Scarlet Family, and we control them.
The enemies variety are mostly the same, with the addition of Spirits and Metal Kedama (like the one in Dragon Quest, rare, loves to escape, gives loads of money). Spirits are annoying, you see, this game has a gimmick: karma. The game doesn't want Youmu to be murdering fellow spirit (fairies and kedama genocide's still fine), so killing spirit increases her karma, higher karma means less strength and defense. But as long as you take care not to kill spirit, you won't get any karma.
The bosses in this game are
hard. As expected, they all use danmaku. It's actually rather difficult to avoid danmaku in platformer, plus Youmu only got her swords to fight them, so that doesn't help. Youmu's rather fast movement speed and jumping momentum makes it hard to dodge, at least her hitbox is small though, that helps. Also, halfway through the game you get dash which allows you to graze them, that also helps. Why can I only adapt to Megamari in terms of platformer bullet hell?
Anyway, just like Touhou, there are 6 bosses + extra. Letty is easy. Chen is probably one of the hardest boss, she bounces all over the room while spraying her trademark danmaku, her movement makes it very hard for her to pin down, and getting close to her means taking a bullet to the face. Alice is pretty simple, 2 of her pattern are easy to dodge, plus she moves toward your x and y position making her easy to bait and attack. Prismriver are jerks, they circle around the very large room while spraying and they all have separate (large) life bar takes takes a while to deplete even if I'm one shotting every enemies in the area. I won with barely any health left (I think only one pixel left). Since Youmu is our character, we'll have Yukkuri boss instead, it's a large target and don't use danmaku, enough said. The final boss ironically is not Yuyuko, instead it's the same yahoos like the previous game, Reimu. She's annoying, her attack is just spraying amulet in your general direction before she stops for 1 second. Circle strafing (in 2 dimension) works best, except unlike Doom Marine, she doesn't have BFG-9000, only her swords + store bought Kirisame sword, so fighting her is just tedious thanks to having to avoid for 80% of the time. In second phase, she adds big amulet into the mix, again, just circle strafe. Third phase is Fantasy Seal and its ridiculous homing, I find it much faster if you just tanks it and slash her face rather than dashing like crazy.
After tackling the main story, you can challenge the extra dungeon if you want to. This requires your karma point to be max, this essentially nuking your str and def. The extra dungeon presents the toughest enemies (made even tougher with nuked stats), their sheer numbers and danmaku can truly challenge you... if I can't cut down bullets and two shot enemies, but they can still takes nearly 2/3 your health bar. The extra boss, which is not Yukari but Sakuya is the hardest boss. She jumps around while spraying slow bullets to you that is easy to avoid but still enough to keep you from slashing her. But that's not why she is hard, she's hard because her attack takes
85% of your health, and that's with me having maxed HP, and she has ridiculous defense that my attack seems to take only 1 pixel of her health bar, and again, that is with me having nearly max strength. Needless to say, I can't beat her. I'm not going to bother with boss that takes 10 minutes to beat where five mistakes at best sends you back.
EDIT: Three games and they couldn't find other final boss than Reimu. That's it, I'm done. In Scarlet Family 2, Reimu is significantly weaker. She doesn't have Fantasy Seal and her bullets can be erased, I curbstomp her... badly. Seriously,
look at this video. (EX-Rumia version)