In water chemistry- there are 3 things that are most important: pH, alkalinity, and a sanitizer. Everything else is ancillary, and to varying degrees.
Those 3 things are of equal importance: Mismanagement of pH and alkalinity causes metals to corrode (jets, heating elements) and that is likely not under warranty. It also reduces the effectiveness of your sanitizer. Your saniziter keeps your water clear and free of algae/bacteria.
Ozone (You said both UV and Ozone but I have to assume you have a UV-based ozonator, as compared to a CD ozonator) generally only kills up to 20% bacteria. So you still need a sanitizer. Plus- Most UV ozonators give out after a year or so, unbeknownst to the user.
Stay way from blanket statements when it comes to sanitizers, when referring to dosage. That is lazy explaining. Think of it like this: How often do you need to buy groceries?
How loaded is that question? You cannot answer w/o knowing how many you are cooking for, how many days, and how many meals/day.
ONLY if you use the spa the exactly the same each time can you say unequivocally that you use "X" and that is all that is needed to be known. The amount of sanitizer is based on how many people are in the spa, how long its used each usage, and how many times a day/days a week. If there is variation to usage habits, you may need more or less sanitizer to be added.
Best bet is to test your spa 2-3 times a week and adjust your sanitizer as necessary. I sell Chlorine, Bromine, Nature II and @ease by King Technology (Spa Frog). They all work well if you know what you're doing. They all have pros and cons. I'll leave it to others to promote a sanitizer as I can work with any of them.
Keep pH, alkalinity and sanitizer levels in line at all times. If you need something to control metals, foam, etc. buy it if that is a problem. But if it isn't a problem yet it may never be a problem so why buy something? Non-chlorine shock may be necessary if you have heavy usage. Metal removers may be needed if you have very hard water. The point is: Keep the important things monitored and if other things require additional chemicals, cross that bridge when you get to it.
Hope this helps. Good luck moving forward.
[Edit: Clarification]