I've finally decided to make the leap and start playing this weird game where you get four cards. 

My background in PLO is maybe about 8-10k hands of lowstakes plo online lifetime, and also some higher stakes ROE in a live setting. Even though PLO has just been played very rarely in between the nlhe grind, I've still watched most of Phil Galfond's PLO videos (both bfp and here). 

I want to get a better feel for the game and see where it can take me if I work hard on theory and analyze my play - basically the same approach as I've had to nlhe. So I have now decided to switch completely over to PLO for a while.

Last two days I've played about 3,2k hands of plo and ran a lot of hands through PPT to get a feel for how equities of different spots run together. When playing though, it's actually been preflop decisions I've been mulling the most over so far. I don't have well defined ranges and end up doing what "feels" right. If I've understood it correctly, PLO is still so far from a game theory optimal solution, that you end up with a lot of different, but winning playing styles. 

This got a little bit long-winded, but over to my question; How should I go about constructing fundamentally sound preflop ranges? In what neighbourhood should my openraise from different positions be? What about the gap between VPIP and PFR? Intuitively it feels like it can be wider than in nlhe, depending on the opposition ofc. 

I'd be very thankful for answers to this, or if you can point me in the right direction as to where I can find this information, it would be much appreciated.