I've had several pieces of Lavacore since I started diving, as well as various spandex dive skin shirts. I have never found any of them to be helpful in putting on a wetsuit versus bare skin. What I have found to be VERY helpful is squirting some diluted baby shampoo in the arms and legs before putting the suit on.
That is one of the main reasons I now have 3, 5, and 7mm wetsuits. The 3 plus Lavacore might be just was warm as a 5mm, but it's a lot easier to lube a 5mm with baby shampoo and put it on over bare skin than to put on the 3mm over a layer of Lavacore. The 5 plus Lavacore might be just as warm as the 7mm, but, again, the 7 is a lot easier to lube and slide on over my bare skin than to slide the 5mm on over the Lavacore.
And at least the Lavacore adds warmth. I gave up on wearing rash guards under a wetsuit. They don't add any warmth and it's a lot easier to leave the guard off and lube the suit to put it on. If I really needed to dive wet, for some reason, and the 7mm was not going to be warm enough by itself, I would add my Lavacore Sleeveless Full Suit. Basically, overalls. I can get my suit up my legs without too much trouble, even over the LC. You can use two hands to get the legs up and adjusted. But, the arms are such a hassle that I would still want to have the wetsuit sliding on over bare arms (with baby shampoo lube).
I really don't like the feeling of bunched up undergarments under my wetsuit. Thus I don't even wear a short sleeve rash guard. Even though mine are tight around my arms and even with the suit lubed, I would still end up with the ends of the sleeves bunched up a bit on my biceps. I also would never wear board shorts under my wetsuit. I wear a Speedo swimsuit (long shorts, like these:
https://www.swimoutlet.com/p/speedo-male-solid-endurance+-jammer-swimsuit-7886/) under the wetsuit. A "briefs" style would probably be even better, but I guess I'm too bashful. I wear board shorts over the swimsuit when I'm out of the wetsuit.
With some diluted baby shampoo in the arms and legs, and wearing nothing but a tight swimsuit, my 7mm wetsuit just slides right on. No muss, no fuss. And it's even to slide around on my body after I get it on, to get it really positioned right.
You (the OP) might end up with something different that works better for you, but I would highly recommend to at least give a try to diving that Neotek with no rash guard and some diluted (50/50) baby shampoo for lube. It's certainly cheap to try. And if you don't like it, you can still keep the baby shampoo solution and use it for mask anti-fog. I keep a sports squeeze bottle filled with diluted baby shampoo in my dive bag. I use it for lube and anti-fog and it's great for both.
