PLO is definitely a higher variance game. You are almost never crushing or are crushed in preflop equity barring AAXX versus lower PPXX.
Even post flop, you often have at least decent equity, that is why people usually bet pot because smaller bets are often giving very good odds
for someone to call. You should almost never be slowplaying anything because of how much people are willing to call and how easy it is for them to get there if you give them a free card. Coolers and flips happen way way more often in PLO than NLHE, thus the higher variance.
NLHE, equities are more lopsided and coolers and flips still do happen but nowhere near as often as PLO.
In short, PLO is much higher variance and it can be very brutal when you keep getting coolered or losing flips. If you have a NLHE background, you may also tend to overvalue a lot of marginal/weak hands in PLO and end up losing alot because of that.
To answer your question luck plays a bigger part in PLO as it is much more forgiving, but that is one of the things that make it more profitable. In PLO, you will see people play much much looser and make bad decisions because they get lucky a few times and think they are doing the right thing.
Both games are profitable at the lowest levels, but NLHE is much easier to pick up for someone who is just starting.You might also not be able to handle the big big swings that is part and parcel of playing PLO if you are new. If you are the type who gets discouraged after a couple coolers in a session, you should stay away from PLO until you can handle variance better.