If your using the 2gb variant of the g5 plus, then you have the same ram as the 5x which also has 2gb ram.
The Lg 5 plus will probably handle things better as it has an upgraded and newer cpu+gpu, so a given would probably be the g5 plus would be better at most everything as compared to the 5x.
I own a 5x, and even today it is no slouch in performance really, but it is a bit dated.
I looked up a few videos of both phones of people doing antutu testing, and some of the videos do geek test, but I just narrowed down to antutu. I'll post the scores from a couple of videos of each phone, with links and timestamps where the scores are, for anyone who wishes to see the difference.
Honestly I was surprised the 5x put out those numbers, they don't seem far from the g5 plus, but I personally would rather own the g5 plus if I had a choice of the two.
Here are the links with scores
5x
AnTuTu Benchmarktest
Video 1: 55330
https://www.youtube.com/watch?v=345eKlssdH8&ytbChannel=null (time frame end of video or 6:59)
Video 2: 63508
https://www.youtube.com/watch?v=67lkw0Pj5Rg&t=244s (time frame 4:02)
g5 plus
AnTuTu Benchmarktest
Video 1: 60154
https://www.youtube.com/watch?v=j8nD_j9OshA&t=6s (time frame 4:17)
video 2: 62769
https://www.youtube.com/watch?v=345eKlssdH8&ytbChannel=null (time frame 5:20) <-----also in spanish but still shows the results score.
Interesting results if your into benchmark scores. I personally am not into benchmark scores because (for me) i think it's just bragging rights, as there are a lot of variables that can make the results of scores, just like on a pc, any settings and such you disable or enable can influence the scores you get, so in the case of phones, you flash a different kernel and overclock, it can drastically affect your score you got, as apposed to someone who has a stock kernel, and not overclocked.
On pc's I've done the oc of both video cards and cpu's game, and I honestly just gave it up, it's more a hobby than anything else.
I've also argued with people who said they can magially see the difference in 60fps vs 100fps, those same people will also swear that they can see a fly in the air and count how many flaps the fly's wings do in a certain time frame (rolls eyes).
For me, I've played games that read 30fps, and ran JUST as smooth as a game that runs at 100-120fps, so it's all relative in my opinion. Take those people, without their oc, their fps counter, and I can almost guarentee you they won't know what fps they are getting and will not be able to tell if you are lagging from low fps or not.
In those rare instances that there IS lag from fps, or performance, then yeah I've seen that too, but thats rare, as lag can also come from bandwidth issues, server side, etc....so many variables to account for, yet people STILL to this day get hung up on the fps kick.
So take stock in what you will, for me, I just see it as a testing tool, or possibly a "just curious" tool and also bragging rights imo, just my 2 cents.