Question: Plants, lights and substrate questions

New owner here, so sorry if this question has been asked 100 times. getting my 1st axol and rather do it right the first time than fix mistakes afterwards. i have a 40 gall breeder tank. want to have sand on the bottom and underwater plants in it as well. so i will need light for the plants. i have read that play sand or pool filter sand is ok to use for both plant substrate and for axol. i heard the axol do not like alot of light since they have no eyelids, so i will have a few caves/cover for them to hang in. question is what plants can go completely underwater and what light can i use that is strong enough to grow plants but not strong enough to hurt my axol? will also have a HOB filter and a splash pad for return water to hit so not to cause a big current.
thanks in advance for any help.

This link should answer all your questions about setups https://www.caudata.org/axolotl-sanctuary/Aquascape.shtml
Scroll down a bit for plants.
I use play sand as my substrate. I've had the most success with java ferns, which don't need to be planted. I've also had anubias, hairgrass, lilaeopsis and banana lillies. And moss balls! In addition to hides I also have a spare strip of tank backing (the plastic background you can stick to the outside of tanks) that sits on the tank cover under the light so it blocks a lot of it, but I can adjust so any plants are getting some light.
As for the light I use an LED. Someone who knows more about lights can probably help more, but it seems to be fine for my tank. I also use the same LED light on my planted (soon to be betta) tank and the plants are growing really well.
Hope that helps