Is there any other shmup in vein of raptor or tyrian or jetsnguns that lets you upgrade or buy new stuff in between mission?

Try this one:
https://www.locomalito.com/hydorah.php

"Weapon selection menu, power ups and unlockable new weapons in every mission."

Have you tried Stargunner?

WinUAE and

Xenon 2 - Mega Blast
X-Out

I follow LocoMalito on Twitter, and even if I have not paid that much atention, from what I read, I think it's still in progress (advancing at quite a pace though) and will not be free, a lá Maldita Castilla Ex (or whatever it was called xD) recently launched


As for recommendations, another vote for Stargunner and totally check Hydorah out (it's free and totally great).
I also have been playing U.N Squadron recently, so if you have MAME, give it a shot.

Been playing stargunner, it's more difficult than the three games I mentioned... Looks like there's very little games like that nowadays...

Well, true, but not surprising considering that shmups is a very niche genre AND those games you mentioned are mostly disliked even amongst the most hardcore shmuppers for their euro-shmuppy mechanics...

For a shop-lite experience I can think of games like Satazius, or Lords of Thunder (weapons can be switched/upgraded btw missions), or Steredenn if a wide variety of weapons is actually what you're looking for in a shop system.

Trouble Witches has mid-stage shops for temporary power ups and stuff. Similar to Forgotten Worlds, Fantasy Zone games...

Well, Astromenace.

But I am sure you'll find something [url=https://en.wikipedia.org/wiki/Category:Vertically_scrolling_shooters]here[/url] too.

Sky Force Anniversary.

Astro Avenger 1 and 2.

Check out 1993 Space Machine.

I would recommend Crimzon Clover - World Ignition. Is not that much similar since you don't buy upgrades or have multiple story paths but damn it, it's amazing :)

Astrotit

Raiden is good. Raiden is always good. Even if it lacks upgrade paths.

The latest ones are mostly on Steam though... oh well... Steredenn and Sky Force are quite close to what I'm looking for, so these goes into the wishlist... (cause you never buy games on steam without heavy discount...)