The main issues with axolotl tanks that are planted are the cold temperatures. I run a low light, low-tech twenty gallon long tank at the moment. My tank: P.H 7.6, Temperature: 68-70. I use Black Diamond Blasting Sand with 20/40 grit as my substrate, it has pretty much no nutrients in it. Your axolotl should fertilize most of the plants for you. Just make sure to keep up with water changes. The low light means that your plants are not going to have very much growth but they will survive.The only other issue is that plants that are rooted in the ground are going to be uprooted at times by the axolotl. Hope I helped.
The plants I have in my tank
Java Moss(Vesicularia dubyana)
Banana Plant(Nymphoides aquatica)
Cryptocorynes(Cryptocoryne parva)
Moneywort(Bacopa monnieri)
Dwarf Hygro(Hygrophila polysperma)
Dwarf Sagitaria (Sagittaria subulata)
Marimo Moss Ball (Aegagropila linnaei)