Gulden is currently at the stage after Dark became Dash and It has the most potential with it's crazy low marketcap for what it already offers users. These guys deliver on all their projects but the one thing they suck at is marketing which is why the coin is doing so badly in price. In terms of development I believe only ETH can match up at this point in time. Here is what they have coming.

https://gulden.com/pow2     --> Witnessing on PoW blocks creating greater security against attacks and being able to earn 20% of the block reward. After the update only 1 confirmation needed due to greater security.
https://gulden.com/SegSig   --> 58% saving on transaction space > Segwit which is only 25%
https://dev.gulden.com/
https://dev.gulden.com/august-development-update/

Oh... and the merchant adoption rate is faster then another other coin besides bitcoin.

http://guldenbites.nl/en/2017/10/01/gulden-in-figures-september/


The above looks great and you probably asking yourselves why is this coin not in the top 100. It really is because they don't hype and market the coin. Development is taking place under the radar kind of like Cyberpunk 2077