If you want repeatability, then you need something that helps you set the angle. If your tools are already sharp, a honing guide can help you with that.
My mostly final solution was a Tormek, which does a great job of helping you set the angle. With the hollow grind, I am then able to free hand on my stones more easily than with a totally flat edge. Obviously your success will vary in that department. So, why do I really like it? While using my chisels, I can very quickly pop over and touch them up free hand and get back to work. I rarely need to go back to the Tormek.
I would expect that with a slow grinder and an setup for setting angles consistently, you could do this without the Tormek, but, the Tormek was the first powered system that provided almost instant success for me.
I used to own a Worksharp system, and many here have had great success with it. I did manage to get things sharp with it, but, I needed to use use a platform on the top (for some reason, I was never able to get the part allowing you to sharpen a chisel from the underside of the disk to work and that was before I was on this forum so I really had nobody to ask). The worst part was that even with the platform, I had significant problems with skewing; which I have not seen anyone mention here before. The reason I had problems I am sure was related to the fact that while using the platform, the edge was placed onto a spinning disk that was running perpendicular to the sharp edge (moving left to right) and I always had problems on that left side. This was my first mechanical sharpening system and I had no idea what I was doing, and although I was able to get sharp edges, I was sufficiently unhappy with the system that I eventually gave it to the husband of my wife's friend who lives a couple of days drive away so I have no idea if he ever used it.
Tormek was my next purchase and I had instant success with chisels and plane blades.
In the years that I have had my Tormek, I have found blades that did not want to sit well in the jig (sides might be uneven, for example) and some very short blades without an appropriate jig, and what if you do not want a hollow grind? And each jig is pretty expensive.
Years ago, I tried to sharpen some knives on my Tormek and was not really happy with the results. Now that I can get a decent edge free hand knife sharpening, I will probably try it again on the Tormek. Note that I had great luck with the WorkSharp knife sharpening systems that use a belt. For keeping it sharp, I also like the Spyderco with the bars held at an angle, but you are not asking about that.
I did not notice where you live, but if you are anywhere near the middle of Ohio, you should try my Tormek and some other things that I have to get a feel for them. I am a big fan of trying a system before you commit, especially if it is a lot of money. If you stick with stones (or similar), decide if you want something that you soak or something that you do not. I did not like soaking my water stones so I currently own Shapton stones that I do not need to soak. I also own diamond stones and lots of Oil stones. There is a different "feel" for all of them. At the end of the day, I get what I feel is the best edge when I go from my Tormek to my Shapton stones 5K (Professional) ending with the 16K glass stone. Some people do not like the feel of the 5K, but having used it for years I don't know any better. I do own a bunch of glass stones (2K, 4K, 6K...) and even an 8K Professional. I don't have a lot of preference, but I generally finish on the 16K if using water stones.
Sometimes, while working, I just keep a few Dans Arkansas stones sitting out. I do not need to worry about them dishing and it leaves a decent edge especially when the chisel is mostly sharp anyway and I just need to clean it up right quick. Flip a coin as to how I will go with it since I own them both.
I usually flatten things on sandpaper so in theory I do not need a bunch of different grits, but I can also use my diamonds if I want. If things are really out of hand, I might use my Norton Crystolon or India stones to get started. Those Crystolon stones are really fast but they leave a rougher surface. I would not do a total final flattening on one if for no other reason than because they wear quickly so probably not as flat. Far more likely to do that for knives that are out of wack if I do not want to use a powered system for some reason.
If you can find someone near you who has a system that you would like to try, I highly recommend that. In the grand scheme of things, a simple guide is not overly expensive and you can use sandpaper on glass (or similar) to get a feel for how that works without spending a bunch. Problem with a Tormek (or similar) is that you just spent a $1000 and if you do not like it, that is a problem.