Just my 2 cents, I have been shooting Caspian framed guns for years. Never had any problems with mags for super or 9mm. The old style mags hold 19 rounds with stock springs and followers. The new style hold 23 with grams springs and followers.
There are a few choices out there for grips, houge, alumagrip and grip tape.
Dawson makes a great mag well for Caspian and if you like a smaller one EGW.
The sight I beleive is a personal choice, nothing wrong with a slide mounted sight if that's what you like but a frame mounted sight is the way to go.
Good luck with your choice, if it runs buy it.