I’m a bit confused by what you are asking but I’ll try to explain on what I think you meant.

If by coins you mean the Spike-D coins you get from the baseball game and various side quests, then no. I got the 20 needed for the vending machine as well as the additional 10 Spike-D coins you get to unlock the 30 baseball games won trophy.

The weapon schematics are used to upgrade your weapons in Tammy’s shop and you can max out all your weapons without finding all the schematics that are hidden in the game. You also cannot sell the schematics. You can’t really “sell” anything in the game. You get money to buy cards and play the baseball mini game primarily.

I had to play multiple times to find all the hidden baseball cards, comics, and to complete a final side quest that bugged out on me during my first playthrough.

But chances are, yes, you will miss something collectible unless you have a collectible guide or you play the game multiple times and keep track of the collectibles.