My water is 7.8 pH as well which is high compared to the ideal but you don't need rodi water just for that. Especially if you want to keep a betta. They are pretty hardy.
For fertilizer look into ThriveC if you don't plan to add pressurized co2.
I don't plan to add pressurized CO2. The expense and the learning curve just don't interest me for such a small tank.
I'm hoping that the Malaysian driftwood does the job. My LFS guy seems to think it will.
I would not add amano shrimp as they like lower pH than you currently have. As stated above bettas (the 'flashy' kinds you see in cups at the store-crowntail, veiltail, halfmoon, delta, plakat, etc etc) will be fine in your pH. I didn't see mention of the tank size? Keep in mind mystery sails make a LOT of poop and need a large tank-10g for just 1, I'd recommend 15g-20g or larger for 2 of those.
btw that lace plant will dominate the tank in time, be ready to trim off leaves as they get too massive.
I know the Madagascar lace will need a lot of trimming but I figure the betta should like it because the leaves sit so high up in the water. Besides, it's much easier to keep neat than that stupid anacharis. I told my daughter when she came home from work today that it's not long for this world.
Dangit about the mystery snails. Everything I've looked at says you can put 2 - 3 in a ten gallon (I updated the information above) if you don't have many other fish. Since I plan to just have a betta I thought it'd be fine. On the other hand I have an Aquaclear 30 on the tank so hopefully the extra filtration will help with the snails.
I know the shrimp won't like the pH which is one of the reasons I'm trying to find a way to lower it. Worst case I cut it with RO/DI water, best case the Malaysian driftwood corrects it. If it becomes too difficult to keep the pH lower and stable then I'll forgo the shrimp.
I do appreciate the information so thank you.