Your 4 hours a week comes out to be ~35 minutes/day. To be honest with you, that's a ton of time to devote to a tank. I spend ~10 minutes a week on maintenance of the tank. This includes manually using a flipper to clean the 3 sides of the tank, siphoning out ~2.5 gallons of water (~12.5% out of 20g aio tank; probably closer to 15% with offset from rocks, sand, etc.), emptying the skimmer cup, and then refilling the tank. When I had the 87G tank up and running, and doing everything manually, it came out to be ~20-30 minutes per week.
With a bigger tank it would take longer, but definitely within your allowable threshold. If you account in for automation with the AWC, then it's more than doable. I do not include feeding the fish (which you can also automate so you can discount this) and observing the tank and corals, since I do not count those as part of time spent on the tank. I count those towards the enjoyment factor of owning a tank instead.
In regards to what you're considering:
With 2 part dosing, there's really hardly any maintenance. The time spent is dependent on how much solution you want to mix and the amount of time you want to spend in between mixing. The amount of solution depends on the size of your dosing containers and how much your corals consume. This is relatively much easier nowadays with automated testing of alk via Trident and other automated alk testing tools. Same applies to even if you were to use a calcium reactor instead.
WC. The bulk of your time on a weekly basis. This takes into consideration the amount of time that you spend mixing the water and the actual time it takes you to do a water change. This is usually something that you do on a weekly basis, at most for the majority of folks. With AWC, you can get away with the occasional manual water change to suck out unwanted detritus/algae, etc. SW can be mixed and stored ahead of time.