Shoulder and back powered hand tools are shit for volume, but awesome for a workout while actually being productive in the process. I hand split my wood now and enjoy the work as much as push mowing my lawn, gives me thinking time while breaking a good sweat. But a decade ago when I had eleven oak trees dropped in my then TN yard by a crew, the smallest of which I still couldn't wrap my arms around, I sure as shit rented a splitter for those massive rounds. In two days of moderate effort I split around five cords that would have taken me months to do by hand. When you need to get the firewood drying for winter burning, you can't wait to do it by hand.
For a good hand splitter, lighter is better as well as find one with a narrow type wedge on the sides, it's very efficient at stressing the wood apart in a smaller area which then forces the rest of the round to separate. Like this:
https://www.homedepot.com/p/Halder-...Axe-with-Superplastic-Face-3007-751/318043454
You don't have to go with the $160 one, but I'm not linking anything up made in China (which are in the ~$50 price range). Easy to find online.
When splitting smaller rounds, up to 15" diameter or so, you need the speed and not the weight. Remember kinetic energy is 1/2 * mass * velocity SQUARED, so the faster you can get your splitter going, the exponential increase in energy to do the work. Anything bigger is where the large and heavy wedge type splitter comes into play, and you get the sledge hammer behind it to do the rest.
A Gränsfors Small Forest Axe is awesome for limbing, or anything else in that size range, as well as being very handy at the camp or a tool for behind the truck seat when you really need it. You can certainly get use out of a full size axe, and get very handy at it as well, but that's on you. There's also a reason so many of us recommend Gränsfors Bruk, worth every penny.
Now for chainsaw recommendations, I'm not touching that Stihl vs. Husqvarna debate...