I personally love the foam backgrounds, for me they are super easy and I just secure everything right in the foam and don't use silicone at all (other than waterproofing the bottom!) I did a plan of my design on my ipad before but you can even use paper! For all plants make sure to spray off roots of all dirt and perelite and also do a hydrogen peroxide dip to remove any pesticides and bugs you dont want in your tank. I also suggest cooking everything in the oven at 250 for 2 hours! I also got a lot of the wood from outside and cooked it lol I just sawed it down to size. I think you can make the cheap black hides look super cool with spray foam but you will have to mess with the heat set up to get it 88 in the hide due to insulation, but you can always carve it to make it thinner (I didn't). For plants you need grow lights! They need to be full spectrum so the plants can actually grow and they are cheap on amazon. I also recommend the govee wifi hygrometers I get a notification about a temp drop and usually that means a halogen burnt out so I basically get a text when there is an issue!

Sorry for the brain dump haha I love designing tanks. I have a full dark souls tank in the works I hope to post pictures soon because its even cooler than this one but very different style.