Solidity is really the standard smart contract language. I'm guessing as far as what most people would expect to know, it would be solidity. Vyper is supposed to have been designed to be more readable and auditable and ultimately more secure but at the cost of some features. I don't know any of the specifics and haven't really programmed much of either. I only lean towards vyper personally because it is a little more like python and therefore a little more comfortable for me.
As far as IDEs, I typically just use vim in a terminal. But I am a nerd, so most people probably wouldn't do that. For python, I have started using PyCharm. I know the pro version offers a lot of other syntax checking including JavaScript. I think JetBrains has a stand-alone JavaScript IDE too. I've never used it though.
Not technically an IDE, but there seems to be some decent love for Atom.
Another one that is pretty popular that I think does JavaScript is Visual Studio Code. I am mostly a Linux purest so have never used it myself, but it seems to have a decent following too.
Eclipse is another one primarily used for Java, however they have plugins for everything and I'm sure JavaScript is one.
There are probably a ton more, those are just the ones with which I am familiar off the top of my head.
I've already downloaded PyCharm and VSCode for JavaScript.
Here's my final choice and my reasoning behind it.
I'll learn JavaScript, HTML and CSS because it appears that there are more local jobs and remote ones as well that require that skill so i'll get over the steep learning curve as quickly as possible.
Then ,as a side hobby, learn the basics of Solidity, which doesn't have a lot of demand yet but i'm assuming that it will be more demand in the future (it's a gamble yeah).