Monero has instant mixing, no masternodes needed.
Yes, the approaches are different. That's pretty much understood.
Yeah, anyone can propose a project for Monero too, we have a forum funding system that already paid several developers. And you know what? These people are paid by donations, NOT by inflation. That's a huge difference... We trust that our community want to invest in the development, you guys need to "steal" from holders of the coin to pay for development by inflating the supply. (or if you loo at it from another angle, you steal from miners and "masternode operators") Did you ever wonder what would happen when there are no more "free coins" to hand out?
The inflation has not increased after the blockchain funding was activated. What do you mean?
Having a funding mechanism built into the protocol doesn't mean a dev couldn't create a gambling site and use the profits for development or people couldn't still donate if their preferred project doesn't get the necessary votes from the network.
InstantX is some kind of "hard mempool". That is not secure. The ledger is written by the miners. So accepting an InstantX is risky.
Nothing is 100% secure. But please elaborate. Could you describe an attack vector that could realistically be used to perform a double spend?